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Journal Cover Plant Molecular Biology
  [SJR: 1.915]   [H-I: 137]   [9 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1573-5028 - ISSN (Online) 0167-4412
   Published by Springer-Verlag Homepage  [2335 journals]
  • The protein phosphatase 2A catalytic subunit StPP2Ac2b acts as a positive
           regulator of tuberization induction in Solanum tuberosum L.
    • Authors: María Noelia Muñiz García; María Catalina Muro; Luciana Carla Mazzocchi; Silvia Marina País; Margarita Stritzler; Mariana Schlesinger; Daniela Andrea Capiati
      Pages: 227 - 245
      Abstract: Key message This study provides the first genetic evidence for the role of PP2A in tuberization, demonstrating that the catalytic subunit StPP2Ac2b positively modulates tuber induction, and that its function is related to the regulation of gibberellic acid metabolism. The results contribute to a better understanding of the molecular mechanism controlling tuberization induction, which remains largely unknown. The serine/threonine protein phosphatases type 2A (PP2A) are implicated in several physiological processes in plants, playing important roles in hormone responses. In cultivated potato (Solanum tuberosum), six PP2A catalytic subunits (StPP2Ac) were identified. The PP2Ac of the subfamily I (StPP2Ac1, 2a and 2b) were suggested to be involved in the tuberization signaling in leaves, where the environmental and hormonal signals are perceived and integrated. The aim of this study was to investigate the role of PP2A in the tuberization induction in stolons. We selected one of the catalytic subunits of the subfamily I, StPP2Ac2b, to develop transgenic plants overexpressing this gene (StPP2Ac2b-OE). Stolons from StPP2Ac2b-OE plants show higher tuber induction rates in vitro, as compared to wild type stolons, with no differences in the number of tubers obtained at the end of the process. This effect is accompanied by higher expression levels of the gibberellic acid (GA) catabolic enzyme StGA2ox1. GA up-regulates StPP2Ac2b expression in stolons, possibly as part of the feedback system by which the hormone regulates its own level. Sucrose, a tuber-promoting factor in vitro, increases StPP2Ac2b expression. We conclude that StPP2Ac2b acts in stolons as a positive regulator tuber induction, integrating different tuberization-related signals mainly though the modulation of GA metabolism.
      PubDate: 2017-02-01
      DOI: 10.1007/s11103-016-0555-7
      Issue No: Vol. 93, No. 3 (2017)
       
  • Metabolo-transcriptome profiling of barley reveals induction of chitin
           elicitor receptor kinase gene ( HvCERK1 ) conferring resistance against
           Fusarium graminearum
    • Authors: Shailesh Karre; Arun Kumar; Dhananjay Dhokane; Ajjamada C. Kushalappa
      Pages: 247 - 267
      Abstract: Key message We report plausible disease resistance mechanisms induced by barley resistant genotype CI89831 against Fusarium head blight (FHB) based on metabolo-transcriptomics approach. We identified HvCERK1 as a candidate gene for FHB resistance, which is functional in resistant genotype CI9831 but non-functional in susceptible cultivars H106-371 and Zhedar-2. For the first time, we were able to show a hierarchy of regulatory genes that regulated downstream biosynthetic genes that eventually produced resistance related metabolites that reinforce the cell walls to contain the pathogen progress in plant. The HvCERK1 can be used for replacing in susceptible commercial cultivars, if non-functional, based on genome editing. Fusarium head blight (FHB) management is a great challenge in barley and wheat production worldwide. Though barley genome sequence and advanced omics technologies are available, till date none of the resistance mechanisms has been clearly deciphered. Hence, this study was aimed at identifying candidate gene(s) and elucidating resistance mechanisms induced by barley resistant genotype CI9831 based on integrated metabolomics and transcriptomics approach. Following Fusarium graminearum infection, we identified accumulation of specific set of induced secondary metabolites, belonging to phenylpropanoid, hydroxycinnamic acid (HCAA) and jasmonic acid pathways, and their biosynthetic genes. In association with these, receptor kinases such as chitin elicitor receptor kinase (HvCERK1) and protein kinases such as MAP kinase 3 (HvMPK3) and MAPK substrate 1 (HvMKS1), and transcription factors such as HvERF1/5, HvNAC42, HvWRKY23 and HvWRKY70 were also found upregulated with high fold change. Polymorphism studies across three barley genotypes confirmed the presence of mutations in HvCERK1 gene in two susceptible genotypes, isolating this gene as a potential candidate for FHB resistance. Further, the silencing of functional HvCERK1 gene in the resistant genotype CI9831, followed by gene expression and metabolite analysis revealed its role as an elicitor recognition receptor that triggered downstream regulatory genes, which in turn, regulated downstream metabolic pathway genes to biosynthesize resistance related (RR) metabolites to contain the pathogen to spikelet infection. A putative model on metabolic pathway regulation is proposed.
      PubDate: 2017-02-01
      DOI: 10.1007/s11103-016-0559-3
      Issue No: Vol. 93, No. 3 (2017)
       
  • A bifunctional aminoglycoside acetyltransferase/phosphotransferase
           conferring tobramycin resistance provides an efficient selectable marker
           for plastid transformation
    • Authors: Iman Tabatabaei; Stephanie Ruf; Ralph Bock
      Pages: 269 - 281
      Abstract: Key message A new selectable marker gene for stable transformation of the plastid genome was developed that is similarly efficient as the aadA, and produces no background of spontaneous resistance mutants. More than 25 years after its development for Chlamydomonas and tobacco, the transformation of the chloroplast genome still represents a challenging technology that is available only in a handful of species. The vast majority of chloroplast transformation experiments conducted thus far have relied on a single selectable marker gene, the spectinomycin resistance gene aadA. Although a few alternative markers have been reported, the aadA has remained unrivalled in efficiency and is, therefore, nearly exclusively used. The development of new marker genes for plastid transformation is of crucial importance to all efforts towards extending the species range of the technology as well as to those applications in basic research, biotechnology and synthetic biology that involve the multistep engineering of plastid genomes. Here, we have tested a bifunctional resistance gene for its suitability as a selectable marker for chloroplast transformation. The bacterial enzyme aminoglycoside acetyltransferase(6′)-Ie/aminoglycoside phosphotransferase(2″)-Ia possesses an N-terminal acetyltransferase domain and a C-terminal phosphotransferase domain that can act synergistically and detoxify aminoglycoside antibiotics highly efficiently. We report that, in combination with selection for resistance to the aminoglycoside tobramycin, the aac(6′)-Ie/aph(2″)-Ia gene represents an efficient marker for plastid transformation in that it produces similar numbers of transplastomic lines as the spectinomycin resistance gene aadA. Importantly, no spontaneous antibiotic resistance mutants appear under tobramycin selection.
      PubDate: 2017-02-01
      DOI: 10.1007/s11103-016-0560-x
      Issue No: Vol. 93, No. 3 (2017)
       
  • The Arabidopsis THO/TREX component TEX1 functionally interacts with MOS11
           and modulates mRNA export and alternative splicing events
    • Authors: Brian B. Sørensen; Hans F. Ehrnsberger; Silvia Esposito; Alexander Pfab; Astrid Bruckmann; Judith Hauptmann; Gunter Meister; Rainer Merkl; Thomas Schubert; Gernot Längst; Michael Melzer; Marion Grasser; Klaus D. Grasser
      Pages: 283 - 298
      Abstract: Key message We identify proteins that associate with the THO core complex, and show that the TEX1 and MOS11 components functionally interact, affecting mRNA export and splicing as well as plant development. TREX (TRanscription-EXport) is a multiprotein complex that plays a central role in the coordination of synthesis, processing and nuclear export of mRNAs. Using targeted proteomics, we identified proteins that associate with the THO core complex of Arabidopsis TREX. In addition to the RNA helicase UAP56 and the mRNA export factors ALY2-4 and MOS11 we detected interactions with the mRNA export complex TREX-2 and multiple spliceosomal components. Plants defective in the THO component TEX1 or in the mRNA export factor MOS11 (orthologue of human CIP29) are mildly affected. However, tex1 mos11 double-mutant plants show marked defects in vegetative and reproductive development. In tex1 plants, the levels of tasiRNAs are reduced, while miR173 levels are decreased in mos11 mutants. In nuclei of mos11 cells increased mRNA accumulation was observed, while no mRNA export defect was detected with tex1 cells. Nevertheless, in tex1 mos11 double-mutants, the mRNA export defect was clearly enhanced relative to mos11. The subnuclear distribution of TEX1 substantially overlaps with that of splicing-related SR proteins and in tex1 plants the ratio of certain alternative splicing events is altered. Our results demonstrate that Arabidopsis TEX1 and MOS11 are involved in distinct steps of the biogenesis of mRNAs and small RNAs, and that they interact regarding some aspects, but act independently in others.
      PubDate: 2017-02-01
      DOI: 10.1007/s11103-016-0561-9
      Issue No: Vol. 93, No. 3 (2017)
       
  • Two MYB-related transcription factors play opposite roles in sugar
           signaling in Arabidopsis
    • Authors: Yi-Shih Chen; Yi-Chi Chao; Tzu-Wei Tseng; Chun-Kai Huang; Pei-Ching Lo; Chung-An Lu
      Pages: 299 - 311
      Abstract: Key message Sugar regulation of gene expression has profound effects at all stages of the plant life cycle. Although regulation at the transcriptional level is one of the most prominent mechanisms by which gene expression is regulated, only a few transcription factors have been identified and demonstrated to be involved in the regulation of sugar-regulated gene expression. OsMYBS1, an R1/2-type MYB transcription factor, has been demonstrated to be involved in sugar- and hormone-regulated α-amylase gene expression in rice. Arabidopsis contains two OsMYBS1 homologs. In the present study, we investigate MYBS1 and MYBS2 in sugar signaling in Arabidopsis. Our results indicate that MYBS1 and MYBS2 play opposite roles in regulating glucose and ABA signaling in Arabidopsis during seed germination and early seedling development. MYB proteins have been classified into four subfamilies: R2R3-MYB, R1/2-MYB, 3R-MYB, and 4R-MYB. An R1/2-type MYB transcription factor, OsMYBS1, has been demonstrated to be involved in sugar- and hormone-regulated α-amylase genes expression in rice. In this study, two genes homologous to OsMYBS1, MYBS1 and MYBS2, were investigated in Arabidopsis. Subcellular localization analysis showed that MYBS1 and MYBS2 were localized in the nucleus. Rice embryo transient expression assays indicated that both MYBS1 and MYBS2 could recognize the sugar response element, TA-box, in the promoter and induced promoter activity. mybs1 mutant exhibited hypersensitivity to glucose, whereas mybs2 seedlings were hyposensitive to it. MYBS1 and MYBS2 are involved in the control of glucose-responsive gene expression, as the mybs1 mutant displayed increased expression of a hexokinase gene (HXK1), chlorophyll a/b-binding protein gene (CAB1), ADP-glucose pyrophosphorylase gene (APL3), and chalcone synthase gene (CHS), whereas the mybs2 mutant exhibited decreased expression of these genes. mybs1 also showed an enhanced response to abscisic acid (ABA) in the seed germination and seedling growth stages, while mybs2 showed reduced responses. The ABA biosynthesis inhibitor fluridone rescued the mybs1 glucose-hypersensitive phenotype. Moreover, the mRNA levels of three ABA biosynthesis genes, ABA1, NCED9, and AAO3, and three ABA signaling genes, ABI3, ABI4, and ABI5, were increased upon glucose treatment of mybs1 seedlings, but were decreased in mybs2 seedlings. These results indicate that MYBS1 and MYBS2 play opposite roles in regulating glucose and ABA signaling in Arabidopsis during seed germination and early seedling development.
      PubDate: 2017-02-01
      DOI: 10.1007/s11103-016-0562-8
      Issue No: Vol. 93, No. 3 (2017)
       
  • Over-expression of miR158 causes pollen abortion in Brassica campestris
           ssp. chinensis
    • Authors: Zhiming Ma; Jianxia Jiang; Ziwei Hu; Tianqi Lyu; Yang Yang; Jingjing Jiang; Jiashu Cao
      Pages: 313 - 326
      Abstract: Key message We identified and cloned the two precursors of miR158 and its target gene in Brassica campestris ssp. chinensis, which both had high relative expression in the inflorescences. Further study revealed that over-expression of miR158 caused reduced pollen varbility, which was caused by the degradation of pollen contents from the binucleate microspore stage. These results first suggest the role of miR158 in pollen development of Brassica campestris ssp. chinensis. MicroRNAs (miRNAs) play crucial roles in many important growth and development processes both in plants and animals by regulating the expression of their target genes via mRNA cleavage or translational repression. In this study, miR158, a Brassicaceae specific miRNA, was functionally characterized with regard to its role in pollen development of non-heading Chinese cabbage (Brassica campestris ssp. chinensis). Two family members of miR158 in B. campestris, namely bra-miR158a1 and bra-miR158a2, and their target gene bra027656, which encodes a pentatricopeptide repeat (PPR) containing protein, were identified. Then, qRT-PCR analysis and GUS-reporter system revealed that both bra-miR158 and its target gene had relatively high expression levels in the inflorescences. Further study revealed that over-expression of miR158 caused reduced pollen varbility and pollen germination ratio, and the degradation of pollen contents from the binucleate microspore stage was also found in those deformed pollen grains, which led to pollen shrinking and collapse in later pollen development stage. These results first shed light on the importance of miR158 in pollen development of Brassica campestris ssp. chinensis.
      PubDate: 2017-02-01
      DOI: 10.1007/s11103-016-0563-7
      Issue No: Vol. 93, No. 3 (2017)
       
  • Phosphate starvation induced OsPHR4 mediates Pi-signaling and homeostasis
           in rice
    • Authors: Wenyuan Ruan; Meina Guo; Ping Wu; Keke Yi
      Pages: 327 - 340
      Abstract: Key message OsPHR4 mediates the regulation of Pi-starvation signaling and Pi-homeostasis in a PHR1-subfamily dependent manner in rice. Phosphate (Pi) starvation response is a sophisticated process for plant in the natural environment. In this process, PHOSPHATE STARVATION RESPONSE 1 (PHR1) subfamily genes play a central role in regulating Pi-starvation signaling and Pi-homeostasis. Besides the three PHR1 orthologs in Oryza sativa L. (Os) [(Os) PHR1, (Os) PHR2, and (Os) PHR3], which were reported to regulated Pi-starvation signaling and Pi-homeostasis redundantly, a close related PHR1 ortholog [designated as (Os) PHR4] is presented in rice genome with unknown function. In this study, we found that OsPHR4 is a Pi-starvation induced gene and mainly expresses in vascular tissues through all growth and development periods. The expression of OsPHR4 is positively regulated by OsPHR1, OsPHR2 and OsPHR3. The nuclear located OsPHR4 can respectively interact with other three PHR1 subfamily members to regulate downstream Pi-starvation induced genes. Consistent with the positive role of PHR4 in regulating Pi-starvation signaling, the OsPHR4 overexpressors display higher Pi accumulation in the shoot and elevated expression of Pi-starvation induced genes under Pi-sufficient condition. Besides, moderate growth retardation and repression of the Pi-starvation signaling in the OsPHR4 RNA interfering (RNAi) transgenic lines can be observed under Pi-deficient condition. Together, we propose that OsPHR4 mediates the regulation of Pi-starvation signaling and Pi-homeostasis in a PHR1-subfamily dependent manner in rice.
      PubDate: 2017-02-01
      DOI: 10.1007/s11103-016-0564-6
      Issue No: Vol. 93, No. 3 (2017)
       
  • Genome-wide identification and characterization of tRNA-derived RNA
           fragments in land plants
    • Authors: Cristiane S. Alves; Renato Vicentini; Gustavo T. Duarte; Vitor F. Pinoti; Michel Vincentz; Fabio T. S. Nogueira
      Pages: 35 - 48
      Abstract: Key message The manuscript by Alves et al. entitled “Genome-wide identification and characterization of tRNA-derived RNA fragments in land plants” describes the identification and characterization of tRNAderived sRNA fragments in plants. By combining bioinformatic analysis and genetic and molecular approaches, we show that tRF biogenesis does not rely on canonical microRNA/siRNA processing machinery (i.e., independent of DICER-LIKE proteins). Moreover, we provide evidences that the Arabidopsis S-like Ribonuclease 1 (RNS1) might be involved in the biogenesis of tRFs. Detailed analyses showed that plant tRFs are sorted into different types of ARGONAUTE proteins and that they have potential target candidate genes. Our work advances the understanding of the tRF biology in plants by providing evidences that plant and animal tRFs shared common features and raising the hypothesis that an interplay between tRFs and other sRNAs might be important to fine-tune gene expression and protein biosynthesis in plant cells. Small RNA (sRNA) fragments derived from tRNAs (3′-loop, 5′-loop, anti-codon loop), named tRFs, have been reported in several organisms, including humans and plants. Although they may interfere with gene expression, their biogenesis and biological functions in plants remain poorly understood. Here, we capitalized on small RNA sequencing data from distinct species such as Arabidopsis thaliana, Oryza sativa, and Physcomitrella patens to examine the diversity of plant tRFs and provide insight into their properties. In silico analyzes of 19 to 25-nt tRFs derived from 5′ (tRF-5s) and 3′CCA (tRF-3s) tRNA loops in these three evolutionary distant species showed that they are conserved and their abundance did not correlate with the number of genomic copies of the parental tRNAs. Moreover, tRF-5 is the most abundant variant in all three species. In silico and in vivo expression analyses unraveled differential accumulation of tRFs in Arabidopsis tissues/organs, suggesting that they are not byproducts of tRNA degradation. We also verified that the biogenesis of most Arabidopsis 19–25 nt tRF-5s and tRF-3s is not primarily dependent on DICER-LIKE proteins, though they seem to be associated with ARGONAUTE proteins and have few potential targets. Finally, we provide evidence that Arabidopsis ribonuclease RNS1 might be involved in the processing and/or degradation of tRFs. Our data support the notion that an interplay between tRFs and other sRNAs might be important to fine tune gene expression and protein biosynthesis in plant cells.
      PubDate: 2017-01-01
      DOI: 10.1007/s11103-016-0545-9
      Issue No: Vol. 93, No. 1-2 (2017)
       
  • Kelch-motif containing acyl-CoA binding proteins AtACBP4 and AtACBP5 are
           differentially expressed and function in floral lipid metabolism
    • Authors: Zi-Wei Ye; Jie Xu; Jianxin Shi; Dabing Zhang; Mee-Len Chye
      Pages: 209 - 225
      Abstract: Key message We herein demonstrated two of the Arabidopsis acyl-CoA-binding proteins (ACBPs), AtACBP4 and AtACBP5, both function in floral lipid metabolism and they may possibly play complementary roles in Arabidopsis microspore-to-pollen development. Histological analysis on transgenic Arabidopsis expressing β-glucuronidase driven from the AtACBP4 and AtACBP5 promoters, as well as, qRTPCR analysis revealed that AtACBP4 was expressed at stages 11–14 in the mature pollen, while AtACBP5 was expressed at stages 7–10 in the microspores and tapetal cells. Immunoelectron microscopy using AtACBP4- or AtACBP5-specific antibodies further showed that AtACBP4 and AtACBP5 were localized in the cytoplasm. Chemical analysis of bud wax and cutin using gas chromatographyflame ionization detector and GC-mass spectrometry analyses revealed the accumulation of cuticular waxes and cutin monomers in acbp4, acbp5 and acbp4acbp5 buds in comparison to the wild type (Col-0). Fatty acid profiling demonstrated a decline in stearic acid and an increase in linolenic acid in acbp4 and acbp4acbp5 buds, respectively, over Col-0. Analysis of inflorescences from acbp4 and acbp5 revealed that there was an increase of AtACBP5 expression in acbp4, and an increase of AtACBP4 expression in acbp5. Deletion analysis of the AtACBP4 and AtACBP5 5′-flanking regions indicated the minimal promoter activity for AtACBP4 (−145/+103) and AtACBP5 (−181/+81). Electrophoretic mobility shift assays identified a pollen-specific cis-acting element POLLEN1 (AGAAA) mapped at AtACBP4 (−157/−153) which interacted with nuclear proteins from flower and this was substantiated by DNase I footprinting. In Arabidopsis thaliana, six acyl-CoA-binding proteins (ACBPs), designated as AtACBP1 to AtACBP6, have been identified to function in plant stress and development. AtACBP4 and AtACBP5 represent the two largest proteins in the AtACBP family. Despite having kelch-motifs and sharing a common cytosolic subcellular localization, AtACBP4 and AtACBP5 differ in spatial and temporal expression. Histological analysis on transgenic Arabidopsis expressing β-glucuronidase driven from the respective AtACBP4 and AtACBP5 promoters, as well as, qRT-PCR analysis revealed that AtACBP4 was expressed at stages 11–14 in mature pollen, while AtACBP5 was expressed at stages 7–10 in the microspores and tapetal cells. Immunoelectron microscopy using AtACBP4- or AtACBP5-specific antibodies further showed that AtACBP4 and AtACBP5 were localized in the cytoplasm. Chemical analysis of bud wax and cutin using gas chromatography-flame ionization detector and GC-mass spectrometry analyses revealed the accumulation of cuticular waxes and cutin monomers in acbp4, acbp5 and acbp4acbp5 buds, in comparison to the wild type. Analysis of inflorescences from acbp4 and acbp5 revealed that there was an increase of AtACBP5 expression in acbp4, and an increase of AtACBP4 expression in acbp5. Deletion analysis of the AtACBP4 and AtACBP5 5′-flanking regions indicated the minimal promoter region for AtACBP4 (−145/+103) and AtACBP5 (−181/+81). Electrophoretic mobility shift assays identified a pollen-specific cis-acting element POLLEN1 (AGAAA) within AtACBP4 (−157/−153) which interacted with nuclear proteins from flower and this was substantiated by DNase I footprinting. These results suggest that AtACBP4 and AtACBP5 both function in floral lipidic metabolism and they may play complementary roles in Arabidopsis microspore-to-pollen development.
      PubDate: 2017-01-01
      DOI: 10.1007/s11103-016-0557-5
      Issue No: Vol. 93, No. 1-2 (2017)
       
  • Association genetics of phenolic needle compounds in Norway spruce with
           variable susceptibility to needle bladder rust
    • Authors: Andrea Ganthaler; Wolfgang Stöggl; Stefan Mayr; Ilse Kranner; Silvio Schüler; Elisabeth Wischnitzki; Eva Maria Sehr; Silvia Fluch; Carlos Trujillo-Moya
      Abstract: Key message Accumulation of phenolic needle metabolites in Norway spruce is regulated by many genes with small and additive effects and is correlated with the susceptibility against fungal attack. Norway spruce accumulates high foliar concentrations of secondary phenolic metabolites, with important functions for pathogen defence responses. However, the molecular genetic basis underlying the quantitative variation of phenolic compounds and their role in enhanced resistance of spruce to infection by needle bladder rust are unknown. To address these questions, a set of 1035 genome-wide single nucleotide polymorphisms (SNPs) was associated to the quantitative variation of four simple phenylpropanoids, eight stilbenes, nine flavonoids, six related arithmetic parameters and the susceptibility to infection by Chrysomyxa rhododendri in an unstructured natural population of Norway spruce. Thirty-one significant genetic associations for the flavonoids gallocatechin, kaempferol 3-glucoside and quercetin 3-glucoside and the stilbenes resveratrol, piceatannol, astringin and isorhapontin were discovered, explaining 22–59% of phenotypic variation, and indicating a regulation of phenolic accumulation by many genes with small and additive effects. The phenolics profile differed between trees with high and low susceptibility to the fungus, underlining the importance of phenolic compounds in the defence mechanisms of Norway spruce to C. rhododendri. Results highlight the utility of association studies in non-model tree species and may enable marker-assisted selection of Norway spruce adapted to severe pathogen attack.
      PubDate: 2017-02-11
      DOI: 10.1007/s11103-017-0589-5
       
  • Wheat drought-responsive WXPL transcription factors regulate cuticle
           biosynthesis genes
    • Authors: Huihui Bi; Sukanya Luang; Yuan Li; Natalia Bazanova; Nikolai Borisjuk; Maria Hrmova; Sergiy Lopato
      Abstract: The cuticle forms a hydrophobic waxy layer that covers plant organs and provides protection from biotic and abiotic stresses. Transcription of genes responsible for cuticle formation is regulated by several types of transcription factors (TFs). Five orthologous to WAX PRODUCTION (WXP1 and WXP2) genes from Medicago truncatula were isolated from a cDNA library prepared from flag leaves and spikes of drought tolerant wheat (Triticum aestivum, breeding line RAC875) and designated TaWXP-like (TaWXPL) genes. Tissue-specific and drought-responsive expression of TaWXPL1D and TaWXPL2B was investigated by quantitative RT-PCR in two Australian wheat genotypes, RAC875 and Kukri, with contrasting glaucousness and drought tolerance. Rapid dehydration and/or slowly developing cyclic drought induced specific expression patterns of WXPL genes in flag leaves of the two cultivars RAC875 and Kukri. TaWXPL1D and TaWXPL2B proteins acted as transcriptional activators in yeast and in wheat cell cultures, and conserved sequences in their activation domains were localised at their C-termini. The involvement of wheat WXPL TFs in regulation of cuticle biosynthesis was confirmed by transient expression in wheat cells, using the promoters of wheat genes encoding two cuticle biosynthetic enzymes, the 3-ketoacyl-CoA-synthetase and the cytochrome P450 monooxygenase. Using the yeast 1-hybrid (Y1H) assay we also demonstrated the differential binding preferences of TaWXPL1D and TaWXPL2B towards three stress-related DNA cis-elements. Protein structural determinants underlying binding selectivity were revealed using comparative 3D molecular modelling of AP2 domains in complex with cis-elements. A scheme is proposed, which links the roles of WXPL and cuticle-related MYB TFs in regulation of genes responsible for the synthesis of cuticle components.
      PubDate: 2017-02-04
      DOI: 10.1007/s11103-017-0585-9
       
  • Depletion of abscisic acid levels in roots of flooded Carrizo citrange (
           Poncirus trifoliata L. Raf. × Citrus sinensis L. Osb.) plants is a
           stress-specific response associated to the differential expression of
           PYR/PYL/RCAR receptors
    • Authors: Vicent Arbona; Sara I. Zandalinas; Matías Manzi; Miguel González-Guzmán; Pedro L. Rodriguez; Aurelio Gómez-Cadenas
      Abstract: Soil flooding reduces root abscisic acid (ABA) levels in citrus, conversely to what happens under drought. Despite this reduction, microarray analyses suggested the existence of a residual ABA signaling in roots of flooded Carrizo citrange seedlings. The comparison of ABA metabolism and signaling in roots of flooded and water stressed plants of Carrizo citrange revealed that the hormone depletion was linked to the upregulation of CsAOG, involved in ABA glycosyl ester (ABAGE) synthesis, and to a moderate induction of catabolism (CsCYP707A, an ABA 8′-hydroxylase) and buildup of dehydrophaseic acid (DPA). Drought strongly induced both ABA biosynthesis and catabolism (CsNCED1, 9-cis-neoxanthin epoxycarotenoid dioxygenase 1, and CsCYP707A) rendering a significant hormone accumulation. In roots of flooded plants, restoration of control ABA levels after stress release was associated to the upregulation of CsBGLU18 (an ABA β-glycosidase) that cleaves ABAGE. Transcriptional profile of ABA receptor genes revealed a different induction in response to soil flooding (CsPYL5) or drought (CsPYL8). These two receptor genes along with CsPYL1 were cloned and expressed in a heterologous system. Recombinant CsPYL5 inhibited ΔNHAB1 activity in vitro at lower ABA concentrations than CsPYL8 or CsPYL1, suggesting its better performance under soil flooding conditions. Both stress conditions induced ABA-responsive genes CsABI5 and CsDREB2A similarly, suggesting the occurrence of ABA signaling in roots of flooded citrus seedlings. The impact of reduced ABA levels in flooded roots on CsPYL5 expression along with its higher hormone affinity reinforce the role of this ABA receptor under soil-flooding conditions and explain the expression of certain ABA-responsive genes.
      PubDate: 2017-02-03
      DOI: 10.1007/s11103-017-0587-7
       
  • Inducible expression of Bs2 R gene from Capsicum chacoense in sweet orange
           ( Citrus sinensis L. Osbeck) confers enhanced resistance to citrus canker
           disease
    • Authors: Lorena Noelia Sendín; Ingrid Georgina Orce; Rocío Liliana Gómez; Ramón Enrique; Carlos Froilán Grellet Bournonville; Aldo Sergio Noguera; Adrián Alberto Vojnov; María Rosa Marano; Atilio Pedro Castagnaro; María Paula Filippone
      Abstract: Transgenic expression of the pepper Bs2 gene confers resistance to Xanthomonas campestris pv. vesicatoria (Xcv) pathogenic strains which contain the avrBs2 avirulence gene in susceptible pepper and tomato varieties. The avrBs2 gene is highly conserved among members of the Xanthomonas genus, and the avrBs2 of Xcv shares 96% homology with the avrBs2 of Xanthomonas citri subsp. citri (Xcc), the causal agent of citrus canker disease. A previous study showed that the transient expression of pepper Bs2 in lemon leaves reduced canker formation and induced plant defence mechanisms. In this work, the effect of the stable expression of Bs2 gene on citrus canker resistance was evaluated in transgenic plants of Citrus sinensis cv. Pineapple. Interestingly, Agrobacterium-mediated transformation of epicotyls was unsuccessful when a constitutive promoter (2× CaMV 35S) was used in the plasmid construction, but seven transgenic lines were obtained with a genetic construction harbouring Bs2 under the control of a pathogen-inducible promoter, from glutathione S-transferase gene from potato. A reduction of disease symptoms of up to 70% was observed in transgenic lines expressing Bs2 with respect to non-transformed control plants. This reduction was directly dependent on the Xcc avrBs2 gene since no effect was observed when a mutant strain of Xcc with a disruption in avrBs2 gene was used for inoculations. Additionally, a canker symptom reduction was correlated with levels of the Bs2 expression in transgenic plants, as assessed by real-time qPCR, and accompanied by the production of reactive oxygen species. These results indicate that the pepper Bs2 resistance gene is also functional in a family other than the Solanaceae, and could be considered for canker control.
      PubDate: 2017-02-02
      DOI: 10.1007/s11103-017-0586-8
       
  • Opposite roles of the Arabidopsis cytokinin receptors AHK2 and AHK3 in the
           expression of plastid genes and genes for the plastid transcriptional
           machinery during senescence
    • Authors: Maria N. Danilova; Natalia V. Kudryakova; Anastasia S. Doroshenko; Dmitry A. Zabrodin; Zulfira F. Rakhmankulova; Ralf Oelmüller; Victor V. Kusnetsov
      Abstract: Key message Cytokinin membrane receptors of the Arabidopsis thaliana AHK2 and AHK3 play opposite roles in the expression of plastid genes and genes for the plastid transcriptional machinery during leaf senescence Loss-of-function mutants of Arabidopsis thaliana were used to study the role of cytokinin receptors in the expression of chloroplast genes during leaf senescence. Accumulation of transcripts of several plastid-encoded genes is dependent on the АНК2/АНК3 receptor combination. АНК2 is particularly important at the final stage of plant development and, unlike АНК3, a positive regulator of leaf senescence. Cytokinin-dependent up-regulation of the nuclear encoded genes for chloroplast RNA polymerases RPOTp and RPOTmp suggests that the hormone controls plastid gene expression, at least in part, via the expression of nuclear genes for the plastid transcription machinery. This is further supported by cytokinin dependent regulation of genes for the nuclear encoded plastid σ-factors, SIG1-6, which code for components of the transcriptional apparatus in chloroplasts.
      PubDate: 2017-02-01
      DOI: 10.1007/s11103-016-0580-6
       
  • Heme oxygenase 1 defects lead to reduced chlorophyll in Brassica napus
    • Authors: Lixia Zhu; Zonghui Yang; Xinhua Zeng; Jie Gao; Jie Liu; Bin Yi; Chaozhi Ma; Jinxiong Shen; Jinxing Tu; Tingdong Fu; Jing Wen
      Abstract: We previously described a Brassica napus chlorophyll-deficient mutant (ygl) with yellow-green seedling leaves and mapped the related gene, BnaC.YGL, to a 0.35 cM region. However, the molecular mechanisms involved in this chlorophyll defect are still unknown. In this study, the BnaC07.HO1 gene (equivalent to BnaC.YGL) was isolated by the candidate gene approach, and its function was confirmed by genetic complementation. Comparative sequencing analysis suggested that BnaC07.HO1 was lost in the mutant, while a long noncoding-RNA was inserted into the promoter of the homologous gene BnaA07.HO1. This insert was widely present in B. napus cultivars and down-regulated BnaA07.HO1 expression. BnaC07.HO1 was highly expressed in the seedling leaves and encoded heme oxygenase 1, which was localized in the chloroplast. Biochemical analysis showed that BnaC07.HO1 can catalyze heme conversion to form biliverdin IXα. RNA-seq analysis revealed that the loss of BnaC07.HO1 impaired tetrapyrrole metabolism, especially chlorophyll biosynthesis. According, the levels of chlorophyll intermediates were reduced in the ygl mutant. In addition, gene expression in multiple pathways was affected in ygl. These findings provide molecular evidences for the basis of the yellow-green leaf phenotype and further insights into the crucial role of HO1 in B. napus.
      PubDate: 2017-01-20
      DOI: 10.1007/s11103-017-0583-y
       
  • Transcriptomic and hormone analyses reveal mechanisms underlying petal
           elongation in Chrysanthemum morifolium ‘Jinba’
    • Authors: Jingjing Wang; Haibin Wang; Lian Ding; Aiping Song; Feng Shen; Jiafu Jiang; Sumei Chen; Fadi Chen
      Abstract: Key message Auxin regulates chrysanthemum petal elongation by promoting cell elongation. Transcriptomic analysis shows that auxin signal transduction may connect with other transcription factors by TCPs to regulate chrysanthemum petal elongation. As an ornamental species, Chrysanthemum morifolium has high ornamental and economic value. Petal size is the primary factor that influences the ornamental value of chrysanthemum, but the mechanism underlying the development of C. morifolium petals remains unclear. In our study, we tracked the growth of petals and found that the basal region of ‘Jinba’ petals showed a higher elongation rate, exhibiting rapid cell elongation during petal growth. During petal elongation growth, auxin was demonstrated to promote cell elongation and an increase in cell numbers in the petal basal region. To further study the molecular mechanisms underlying petal growth, the RNA-seq (high-throughput cDNA sequencing) technique was employed. Four cDNA libraries were assembled from petals in the budding, bud breaking, early blooming and full blooming stages of ‘Jinba’ flower development. Analysis of differentially expressed genes (DEGs) showed that auxin was the most important regulator in controlling petal growth. The TEOSINTEBRANCHED 1, CYCLOIDEA and PCF transcription factor genes (TCPs), basic helix-loop-helix-encoding gene (bHLH), glutaredoxin-C (GRXC) and other zinc finger protein genes exhibited obvious up-regulation and might have significant effects on the growth of ‘Jinba’ petals. Given the interaction between these genes in Arabidopsis thaliana, we speculated that auxin signal transduction might exhibit a close relationship with transcription factors through TCPs. In summary, we present the first comprehensive transcriptomic and hormone analyses of C. morifolium petals. The results offer direction in identifying the mechanism underlying the development of chrysanthemum petals in the elongated phase and have great significance in improving the ornamental characteristics of C. morifolium via molecular breeding.
      PubDate: 2017-01-20
      DOI: 10.1007/s11103-017-0584-x
       
  • Retraction note to: Brassica RNA binding protein ERD4 is involved in
           conferring salt, drought tolerance and enhancing plant growth in
           Arabidopsis
    • Authors: Archana N. Rai; Srinath Tamirisa; K. V. Rao; Vinay Kumar; P. Suprasanna
      PubDate: 2017-01-18
      DOI: 10.1007/s11103-016-0574-4
       
  • The mobile RNAs, StBEL11 and StBEL29 , suppress growth of tubers in potato
    • Authors: Tejashree H. Ghate; Pooja Sharma; Kirtikumar R. Kondhare; David J. Hannapel; Anjan K. Banerjee
      Abstract: Key message We demonstrate that RNAs of StBEL11 and StBEL29 are phloem-mobile and function antagonistically to the growth-promoting characteristics of StBEL5 in potato. Both these RNAs appear to inhibit tuber growth by repressing the activity of target genes of StBEL5 in potato. Moreover, upstream sequence driving GUS expression in transgenic potato lines demonstrated that both StBEL11 and -29 promoter activity is robust in leaf veins, petioles, stems, and vascular tissues and induced by short days in leaves and stolons. Steady-state levels of their mRNAs were also enhanced by short-day conditions in selective organs. There are thirteen functional BEL1-like genes in potato that encode for a family of transcription factors (TF) ubiquitous in the plant kingdom. These BEL1 TFs work in tandem with KNOTTED1-types to regulate the expression of numerous target genes involved in hormone metabolism and growth processes. One of the StBELs, StBEL5, functions as a long-distance mRNA signal that is transcribed in leaves and moves into roots and stolons to stimulate growth. The two most closely related StBELs to StBEL5 are StBEL11 and -29. Together these three genes make up more than 70% of all StBEL transcripts present throughout the potato plant. They share a number of common features, suggesting they may be co-functional in tuber development. Upstream sequence driving GUS expression in transgenic potato lines demonstrated that both StBEL11 and -29 promoter activity is robust in leaf veins, petioles, stems, and vascular tissues and induced by short-days in leaves and stolons. Steady-state levels of their mRNAs were also enhanced by short-day conditions in specific organs. Using a transgenic approach and heterografting experiments, we show that both these StBELs inhibit growth in correlation with the long distance transport of their mRNAs from leaves to roots and stolons, whereas suppression lines of these two RNAs exhibited enhanced tuber yields. In summary, our results indicate that the RNAs of StBEL11 and StBEL29 are phloem-mobile and function antagonistically to the growth-promoting characteristics of StBEL5. Both these RNAs appear to inhibit growth in tubers by repressing the activity of target genes of StBEL5.
      PubDate: 2017-01-13
      DOI: 10.1007/s11103-016-0582-4
       
  • The monomeric GTPase RabA2 is required for progression and maintenance of
           membrane integrity of infection threads during root nodule symbiosis
    • Authors: Virginia Dalla Via; Soledad Traubenik; Claudio Rivero; O. Mario Aguilar; María Eugenia Zanetti; Flavio Antonio Blanco
      Abstract: Key message Progression of the infection canal that conducts rhizobia to the nodule primordium requires a functional Rab GTPase located in Golgi/trans-Golgi that also participate in root hair polar growth. Common bean (Phaseolus vulgaris) symbiotically associates with its partner Rhizobium etli, resulting in the formation of root nitrogen-fixing nodules. Compatible bacteria can reach cortical cells in a tightly regulated infection process, in which the specific recognition of signal molecules is a key step to select the symbiotic partner. In this work, we show that RabA2, a monomeric GTPase from common bean, is required for the progression of the infection canal, referred to as the infection thread (IT), toward the cortical cells. Expression of miss-regulated mutant variants of RabA2 resulted in an increased number of abortive infection events, including bursting of ITs and a reduction in the number of nodules. Nodules formed in these plants were small and contained infected cells with disrupted symbiosome membranes, indicating either early senescence of these cells or defects in the formation of the symbiosome membrane during bacterial release. RabA2 localized to mobile vesicles around the IT, but mutations that affect GTP hydrolysis or GTP/GDP exchange modified this localization. Colocalization of RabA2 with ArfA1 and a Golgi marker indicates that RabA2 localizes in Golgi stacks and the trans-Golgi network. Our results suggest that RabA2 is part of the vesicle transport events required to maintain the integrity of the membrane during IT progression.
      PubDate: 2017-01-10
      DOI: 10.1007/s11103-016-0581-5
       
  • Reviewer acknowledgments
    • PubDate: 2017-01-05
      DOI: 10.1007/s11103-016-0577-1
       
 
 
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