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Journal Cover Plant Molecular Biology
  [SJR: 1.915]   [H-I: 137]   [7 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  [2350 journals]
  • RAP2.6L and jasmonic acid–responsive genes are expressed upon
           Arabidopsis hypocotyl grafting but are not needed for cell proliferation
           related to healing
    • Authors: Keita Matsuoka; Raiki Yanagi; Emi Yumoto; Takao Yokota; Hisakazu Yamane; Shinobu Satoh; Masashi Asahina
      Pages: 531 - 542
      Abstract: Key message Jasmonic acid and RAP2.6L are induced upon wounding but are not involved in cell proliferation during healing in Arabidopsis hypocotyls. Plants produce jasmonic acid in response to wounding, but its role in healing, if any, has not been determined. Previously, the jasmonic acid–induced transcription factor, RAP2.6L, related to APETALA 2.6-like, was identified as a spatially expressed factor involved in tissue reunion in partially incised flowering stems of Arabidopsis. In the present study, we investigated the function of JA and RAP2.6L on wound healing using an Arabidopsis hypocotyl-grafting system, in which separated tissues are reattached by vascular tissue cell proliferation. The jasmonic acid–responsive genes AOS and JAZ10 were transiently expressed immediately after grafting. We confirmed that the endogenous content of jasmonic acid-Ile, which is the bioactive form of jasmonic acid, increased in hypocotyls 1 h after grafting. Morphological analysis of the grafted tissue revealed that vascular tissue cell proliferation occurred in a similar manner in wild-type Arabidopsis, the jasmonic acid–deficient mutant aos, the jasmonic acid–insensitive mutant coi1, and in Arabidopsis that had been exogenously treated with jasmonic acid. RAP2.6L expression was also induced during graft healing. Because RAP2.6L expression occurred during graft healing in aos and coi1, its expression must be regulated via a jasmonic acid–independent pathway. The rap2.6L mutant and dominant repressor transformants for RAP2.6L showed normal cell proliferation during graft healing. Taken together, our results suggest that JA and RAP2.6L, induced by grafting, are not necessary for cell proliferation process in healing.
      PubDate: 2018-04-01
      DOI: 10.1007/s11103-018-0702-4
      Issue No: Vol. 96, No. 6 (2018)
       
  • Tea plant SWEET transporters: expression profiling, sugar transport, and
           the involvement of CsSWEET16 in modifying cold tolerance in Arabidopsis
    • Authors: Lu Wang; Lina Yao; Xinyuan Hao; Nana Li; Wenjun Qian; Chuan Yue; Changqing Ding; Jianming Zeng; Yajun Yang; Xinchao Wang
      Pages: 577 - 592
      Abstract: Key message Thirteen SWEET transporters were identified in Camellia sinensis and the cold-suppression gene CsSWEET16 contributed to sugar compartmentation across the vacuole and function in modifying cold tolerance in Arabidopsis. The sugars will eventually be exported transporters (SWEET) family of sugar transporters in plants is a recently identified protein family of sugar uniporters that contain seven transmembrane helices harbouring two MtN3 motifs. SWEETs play important roles in various biological processes, including plant responses to environmental stimuli. In this study, 13 SWEET transporters were identified in Camellia sinensis and were divided into four clades. Transcript abundances of CsSWEET genes were detected in various tissues. CsSWEET1a/1b/2a/2b/2c/3/9b/16/17 were expressed in all of the selected tissues, whereas the expression of CsSWEET5/7/9a/15 was not detected in some tissues, including those of mature leaves. Expression analysis of nine CsSWEET genes in leaves in response to abiotic stresses, natural cold acclimation and Colletotrichum camelliae infection revealed that eight CsSWEET genes responded to abiotic stress, while CsSWEET3 responded to C. camelliae infection. Functional analysis of 13 CsSWEET activities in yeast revealed that CsSWEET1a/1b/7/17 exhibit transport activity for glucose analogues and other types of hexose molecules. Further characterization of the cold-suppression gene CsSWEET16 revealed that this gene is localized in the vacuolar membrane. CsSWEET16 contributed to sugar compartmentation across the vacuole and function in modifying cold tolerance in Arabidopsis. Together, these findings demonstrate that CsSWEET genes play important roles in the response to abiotic and biotic stresses in tea plants and provide insights into the characteristics of SWEET genes in tea plants, which could serve as the basis for further functional identification of such genes.
      PubDate: 2018-04-01
      DOI: 10.1007/s11103-018-0716-y
      Issue No: Vol. 96, No. 6 (2018)
       
  • TaEDS1 genes positively regulate resistance to powdery mildew in wheat
    • Authors: Guiping Chen; Bo Wei; Guoliang Li; Caiyan Gong; Renchun Fan; Xiangqi Zhang
      Pages: 607 - 625
      Abstract: Key message Three EDS1 genes were cloned from common wheat and were demonstrated to positively regulate resistance to powdery mildew in wheat. The EDS1 proteins play important roles in plant basal resistance and TIR-NB-LRR protein-triggered resistance in dicots. Until now, there have been very few studies on EDS1 in monocots, and none in wheat. Here, we report on three common wheat orthologous genes of EDS1 family (TaEDS1-5A, 5B and 5D) and their function in powdery mildew resistance. Comparisons of these genes with their orthologs in diploid ancestors revealed that EDS1 is a conserved gene family in Triticeae. The cDNA sequence similarity among the three TaEDS1 genes was greater than 96.5%, and they shared sequence similarities of more than 99.6% with the respective orthologs from diploid ancestors. The phylogenetic analysis revealed that the EDS1 family originated prior to the differentiation of monocots and dicots, and EDS1 members have since undergone clear structural differentiation. The transcriptional levels of TaEDS1 genes in the leaves were obviously higher than those of the other organs, and they were induced by Blumeria graminis f. sp. tritici (Bgt) infection and salicylic acid (SA) treatment. The BSMV-VIGS experiments indicated that knock-down the transcriptional levels of the TaEDS1 genes in a powdery mildew-resistant variety of common wheat compromised resistance. Contrarily, transient overexpression of TaEDS1 genes in a susceptible common wheat variety significantly reduced the haustorium index and attenuated the growth of Bgt. Furthermore, the expression of TaEDS1 genes in the Arabidopsis mutant eds1-1 complemented its susceptible phenotype to powdery mildew. The above evidences strongly suggest that TaEDS1 acts as a positive regulator and confers resistance against powdery mildew in common wheat.
      PubDate: 2018-04-01
      DOI: 10.1007/s11103-018-0718-9
      Issue No: Vol. 96, No. 6 (2018)
       
  • miRNAs control HAM1 functions at the single-cell-layer level and are
           essential for normal embryogenesis in Arabidopsis
    • Authors: Hideki Takanashi; Hikari Sumiyoshi; Mirai Mogi; Yoshikazu Hayashi; Takayuki Ohnishi; Nobuhiro Tsutsumi
      Pages: 627 - 640
      Abstract: Key message miR171a controls HAM1 functions within the protodermal cells of the embryo, and these controls are essential for normal embryogenesis in Arabidopsis. Arabidopsis thaliana miR171a is known to bind to and cleave mRNAs of three HAIRY MERISTEM (HAM) genes that encode members of the GRAS family transcriptional regulators. The molecular functions of the HAM genes are still being elucidated in Arabidopsis. However, detailed expression patterns of miR171a and the effects of the failure of miR171a to suppress HAM genes were unknown till now. Here, we show the detailed expression patterns of miR171a and HAM1 using green fluorescent protein and confocal scanning microscopy. Our observations revealed that miR171a was expressed in the surface cell layer of the embryo and shoot apical meristem, and it controlled HAM1 functions. To determine the impact of the failure of miR171a to suppress of HAM1, we introduced seven synonymous mutations into the miR171a target site of the HAM1 gene (modified HAM1, mHAM1) and generated transgenic plants that had mHAM1 driven by HAM1 native promoter. The mHAM1 transgenic plants showed organogenic defects. These results indicate that the control of HAM1 functions at the single-cell-layer level by miR171a is essential for proper organ formation in Arabidopsis.
      PubDate: 2018-04-01
      DOI: 10.1007/s11103-018-0719-8
      Issue No: Vol. 96, No. 6 (2018)
       
  • Tracking the elusive 5′ exonuclease activity of Chlamydomonas
           reinhardtii RNase J
    • Authors: Anna Liponska; Ailar Jamalli; Richard Kuras; Loreto Suay; Enrico Garbe; Francis-André Wollman; Soumaya Laalami; Harald Putzer
      Pages: 641 - 653
      Abstract: Key message Chlamydomonas RNase J is the first member of this enzyme family that has endo- but no intrinsic 5′ exoribonucleolytic activity. This questions its proposed role in chloroplast mRNA maturation. RNA maturation and stability in the chloroplast are controlled by nuclear-encoded ribonucleases and RNA binding proteins. Notably, mRNA 5′ end maturation is thought to be achieved by the combined action of a 5′ exoribonuclease and specific pentatricopeptide repeat proteins (PPR) that block the progression of the nuclease. In Arabidopsis the 5′ exo- and endoribonuclease RNase J has been implicated in this process. Here, we verified the chloroplast localization of the orthologous Chlamydomonas (Cr) RNase J and studied its activity, both in vitro and in vivo in a heterologous B. subtilis system. Our data show that Cr RNase J has endo- but no significant intrinsic 5′ exonuclease activity that would be compatible with its proposed role in mRNA maturation. This is the first example of an RNase J ortholog that does not possess a 5′ exonuclease activity. A yeast two-hybrid screen revealed a number of potential interaction partners but three of the most promising candidates tested, failed to induce the latent exonuclease activity of Cr RNase J. We still favor the hypothesis that Cr RNase J plays an important role in RNA metabolism, but our findings suggest that it rather acts as an endoribonuclease in the chloroplast.
      PubDate: 2018-04-01
      DOI: 10.1007/s11103-018-0720-2
      Issue No: Vol. 96, No. 6 (2018)
       
  • The Arabidopsis histone chaperone FACT is required for stress-induced
           expression of anthocyanin biosynthetic genes
    • Authors: Alexander Pfab; Matthias Breindl; Klaus D. Grasser
      Pages: 367 - 374
      Abstract: Key message The histone chaperone FACT is involved in the expression of genes encoding anthocyanin biosynthetic enzymes also upon induction by moderate high-light and therefore contributes to the stress-induced plant pigmentation. The histone chaperone FACT consists of the SSRP1 and SPT16 proteins and associates with transcribing RNAPII (RNAPII) along the transcribed region of genes. FACT can promote transcriptional elongation by destabilising nucleosomes in the path of RNA polymerase II, thereby facilitating efficient transcription of chromatin templates. Transcript profiling of Arabidopsis plants depleted in SSRP1 or SPT16 demonstrates that only a small subset of genes is differentially expressed relative to wild type. The majority of these genes is either up- or down-regulated in both the ssrp1 and spt16 plants. Among the down-regulated genes, those encoding enzymes of the biosynthetic pathway of the plant secondary metabolites termed anthocyanins (but not regulators of the pathway) are overrepresented. Upon exposure to moderate high-light stress several of these genes are up-regulated to a lesser extent in ssrp1/spt16 compared to wild type plants, and accordingly the mutant plants accumulate lower amounts of anthocyanin pigments. Moreover, the expression of SSRP1 and SPT16 is induced under these conditions. Therefore, our findings indicate that FACT is a novel factor required for the accumulation of anthocyanins in response to light-induction.
      PubDate: 2018-03-01
      DOI: 10.1007/s11103-018-0701-5
      Issue No: Vol. 96, No. 4-5 (2018)
       
  • TALEN-mediated targeted mutagenesis of fatty acid desaturase 2 ( FAD2 ) in
           peanut ( Arachis hypogaea L.) promotes the accumulation of oleic acid
    • Authors: Shijie Wen; Hao Liu; Xingyu Li; Xiaoping Chen; Yanbin Hong; Haifen Li; Qing Lu; Xuanqiang Liang
      Abstract: Key message A first creation of high oleic acid peanut varieties by using transcription activator-like effecter nucleases (TALENs) mediated targeted mutagenesis of Fatty Acid Desaturase 2 (FAD2). Transcription activator like effector nucleases (TALENs), which allow the precise editing of DNA, have already been developed and applied for genome engineering in diverse organisms. However, they are scarcely used in higher plant study and crop improvement, especially in allopolyploid plants. In the present study, we aimed to create targeted mutagenesis by TALENs in peanut. Targeted mutations in the conserved coding sequence of Arachis hypogaea fatty acid desaturase 2 (AhFAD2) were created by TALENs. Genetic stability of AhFAD2 mutations was identified by DNA sequencing in up to 9.52 and 4.11% of the regeneration plants at two different targeted sites, respectively. Mutation frequencies among AhFAD2 mutant lines were significantly correlated to oleic acid accumulation. Genetically, stable individuals of positive mutant lines displayed a 0.5–2 fold increase in the oleic acid content compared with non-transgenic controls. This finding suggested that TALEN-mediated targeted mutagenesis could increase the oleic acid content in edible peanut oil. Furthermore, this was the first report on peanut genome editing event, and the obtained high oleic mutants could serve for peanut breeding project.
      PubDate: 2018-04-26
      DOI: 10.1007/s11103-018-0731-z
       
  • An improved ternary vector system for Agrobacterium -mediated rapid maize
           transformation
    • Authors: Ajith Anand; Steven H. Bass; Emily Wu; Ning Wang; Kevin E. McBride; Narayana Annaluru; Michael Miller; Mo Hua; Todd J. Jones
      Abstract: Key message A simple and versatile ternary vector system that utilizes improved accessory plasmids for rapid maize transformation is described. This system facilitates high-throughput vector construction and plant transformation. The super binary plasmid pSB1 is a mainstay of maize transformation. However, the large size of the base vector makes it challenging to clone, the process of co-integration is cumbersome and inefficient, and some Agrobacterium strains are known to give rise to spontaneous mutants resistant to tetracycline. These limitations present substantial barriers to high throughput vector construction. Here we describe a smaller, simpler and versatile ternary vector system for maize transformation that utilizes improved accessory plasmids requiring no co-integration step. In addition, the newly described accessory plasmids have restored virulence genes found to be defective in pSB1, as well as added virulence genes. Testing of different configurations of the accessory plasmids in combination with T-DNA binary vector as ternary vectors nearly doubles both the raw transformation frequency and the number of transformation events of usable quality in difficult-to-transform maize inbreds. The newly described ternary vectors enabled the development of a rapid maize transformation method for elite inbreds. This vector system facilitated screening different origins of replication on the accessory plasmid and T-DNA vector, and four combinations were identified that have high (86–103%) raw transformation frequency in an elite maize inbred.
      PubDate: 2018-04-23
      DOI: 10.1007/s11103-018-0732-y
       
  • Role of Arabidopsis ABF1 / 3 / 4 during det1 germination in salt and
           osmotic stress conditions
    • Authors: V. C. Dilukshi Fernando; Wesam Al Khateeb; Mark F. Belmonte; Dana F. Schroeder
      Abstract: Key message Arabidopsis det1 mutants exhibit salt and osmotic stress resistant germination. This phenotype requires HY5, ABF1, ABF3, and ABF4. While DE-ETIOLATED 1 (DET1) is well known as a negative regulator of light development, here we describe how det1 mutants also exhibit altered responses to salt and osmotic stress, specifically salt and mannitol resistant germination. LONG HYPOCOTYL 5 (HY5) positively regulates both light and abscisic acid (ABA) signalling. We found that hy5 suppressed the det1 salt and mannitol resistant germination phenotype, thus, det1 stress resistant germination requires HY5. We then queried publically available microarray datasets to identify genes downstream of HY5 that were differentially expressed in det1 mutants. Our analysis revealed that ABA regulated genes, including ABA RESPONSIVE ELEMENT BINDING FACTOR 3 (ABF3), are downregulated in det1 seedlings. We found that ABF3 is induced by salt in wildtype seeds, while homologues ABF4 and ABF1 are repressed, and all three genes are underexpressed in det1 seeds. We then investigated the role of ABF3, ABF4, and ABF1 in det1 phenotypes. Double mutant analysis showed that abf3, abf4, and abf1 all suppress the det1 salt/osmotic stress resistant germination phenotype. In addition, abf1 suppressed det1 rapid water loss and open stomata phenotypes. Thus interactions between ABF genes contribute to det1 salt/osmotic stress response phenotypes.
      PubDate: 2018-04-21
      DOI: 10.1007/s11103-018-0729-6
       
  • Molecular identification of GAPDHs in cassava highlights the antagonism of
           MeGAPCs and MeATG8s in plant disease resistance against cassava bacterial
           blight
    • Authors: Hongqiu Zeng; Yanwei Xie; Guoyin Liu; Daozhe Lin; Chaozu He; Haitao Shi
      Abstract: Key message MeGAPCs were identified as negative regulators of plant disease resistance, and the interaction of MeGAPCs and MeATG8s was highlighted in plant defense response. As an important enzyme of glycolysis metabolic pathway, glyceraldehyde-3-P dehydrogenase (GAPDH) plays important roles in plant development, abiotic stress and immune responses. Cassava (Manihot esculenta) is most important tropical crop and one of the major food crops, however, no information is available about GAPDH gene family in cassava. In this study, 14 MeGAPDHs including 6 cytosol GAPDHs (MeGAPCs) were identified from cassava, and the transcripts of 14 MeGAPDHs in response to Xanthomonas axonopodis pv manihotis (Xam) indicated their possible involvement in immune responses. Further investigation showed that MeGAPCs are negative regulators of disease resistance against Xam. Through transient expression in Nicotiana benthamiana, we found that overexpression of MeGAPCs led to decreased disease resistance against Xam. On the contrary, MeGAPCs-silenced cassava plants through virus-induced gene silencing (VIGS) conferred improved disease resistance. Notably, MeGAPCs physically interacted with autophagy-related protein 8b (MeATG8b) and MeATG8e and inhibited autophagic activity. Moreover, MeATG8b and MeATG8e negatively regulated the activities of NAD-dependent MeGAPDHs, and are involved in MeGAPCs-mediated disease resistance. Taken together, this study highlights the involvement of MeGAPCs in plant disease resistance, through interacting with MeATG8b and MeATG8e.
      PubDate: 2018-04-20
      DOI: 10.1007/s11103-018-0733-x
       
  • The zinc-finger transcription factor ZAT6 is essential for hydrogen
           peroxide induction of anthocyanin synthesis in Arabidopsis
    • Authors: Haitao Shi; Guoyin Liu; Yunxie Wei; Zhulong Chan
      Abstract: The accumulation of flavonoids is activated by various abiotic stresses, and the induction of reactive oxygen species (ROS) especially hydrogen peroxide (H2O2) is a general response to abiotic stress in plants. However, the direct link between flavonoids and H2O2 and underlying mechanism remain elusive. In this study, we found that the concentrations of anthocyanin and flavonoids were significantly induced by H2O2 treatment. Furthermore, we found that the transcript level of ZINC FINGER of ARABIDOPSIS THALIANA 6 (ZAT6) was significantly activated after exogenous H2O2 treatment, and modulation of AtZAT6 expression positively affected the concentrations of both anthocyanin and total flavonoids. Notably, exogenous H2O2-induced anthocyanin synthesis was largely alleviated in AtZAT6 knockdown plants, but showed higher level in AtZAT6 overexpressing plants. AtZAT6 directly activated the expressions of TT5, TT7, TT3, TT18, MYB12, and MYB111 through binding to their promoters with TACAAT elements of these genes, and the activation of MYB12 and MYB111 up-regulated the expressions of TT4 and TT6. Taken together, this study indicates that AtZAT6 plays important role in H2O2-activated anthocyanin synthesis, via directly binding to the promoters of several genes that involved in anthocyanin synthesis.
      PubDate: 2018-04-19
      DOI: 10.1007/s11103-018-0730-0
       
  • A novel mitochondrial orf147 causes cytoplasmic male sterility in
           pigeonpea by modulating aberrant anther dehiscence
    • Authors: Pooja Bhatnagar-Mathur; Ranadheer Gupta; Palakolanu Sudhakar Reddy; Bommineni Pradeep Reddy; Dumbala Srinivas Reddy; C. V. Sameerkumar; Rachit Kumar Saxena; Kiran K. Sharma
      Abstract: Key message A novel open reading frame (ORF) identified and cloned from the A4 cytoplasm of Cajanus cajanifolius induced partial to complete male sterility when introduced into Arabidopsis and tobacco. Pigeonpea (Cajanus cajan L. Millsp.) is the only legume known to have commercial hybrid seed technology based on cytoplasmic male sterility (CMS). We identified a novel ORF (orf147) from the A4 cytoplasm of C. cajanifolius that was created via rearrangements in the CMS line and co-transcribes with the known and unknown sequences. The bi/poly-cistronic transcripts cause gain-of-function variants in the mitochondrial genome of CMS pigeonpea lines having distinct processing mechanisms and transcription start sites. In presence of orf147, significant repression of Escherichia coli growth indicated its toxicity to the host cells and induced partial to complete male sterility in transgenic progenies of Arabidopsis thaliana and Nicotiana tabacum where phenotype co-segregated with the transgene. The male sterile plants showed aberrant floral development and reduced lignin content in the anthers. Gene expression studies in male sterile pigeonpea, Arabidopsis and tobacco plants confirmed down-regulation of several anther biogenesis genes and key genes involved in monolignol biosynthesis, indicative of regulation of retrograde signaling. Besides providing evidence for the involvement of orf147 in pigeonpea CMS, this study provides valuable insights into its function. Cytotoxicity and aberrant programmed cell death induced by orf147 could be important for mechanism underlying male sterility that offers opportunities for possible translation for these findings for exploiting hybrid vigor in other recalcitrant crops as well.
      PubDate: 2018-04-17
      DOI: 10.1007/s11103-018-0728-7
       
  • Expression of VGRNb-PE immunotoxin in transplastomic lettuce ( Lactuca
           sativa L.)
    • Authors: Malihe Mirzaee; Mokhtar Jalali-Javaran; Ahmad Moieni; Sirous Zeinali; Mahdi Behdani
      Abstract: Key message This research has shown, for the first time, that plant chloroplasts are a suitable compartment for synthesizing recombinant immunotoxins and the transgenic immunotoxin efficiently causes the inhibition of VEGFR2 overexpression, cell growth and proliferation. Angiogenesis refers to the formation of new blood vessels, which resulted in the growth, invasion and metastasis of cancer. The vascular endothelial growth factor receptor 2 (VEGFR2) plays a major role in angiogenesis and blocking of its signaling inhibits neovascularization and tumor metastasis. Immunotoxins are promising therapeutics for targeted cancer therapy. They consist of an antibody linked to a protein toxin and are designed to specifically kill the tumor cells. In our previous study, VGRNb-PE immunotoxin protein containing anti-VEGFR2 nanobody fused to the truncated form of Pseudomonas exotoxin A has been established. Here, we expressed this immunotoxin in lettuce chloroplasts. Chloroplast genetic engineering offers several advantages, including high levels of transgene expression, multigene engineering in a single transformation event and maternal inheritance of the transgenes. Site specific integration of transgene into chloroplast genomes, and homoplasmy were confirmed. Immunotoxin levels reached up to 1.1% of total soluble protein or 33.7 µg per 100 mg of leaf tissue (fresh weight). We demonstrated that transgenic immunotoxin efficiently causes the inhibition of VEGFR2 overexpression, cell growth and proliferation. These results indicate that plant chloroplasts are a suitable compartment for synthesizing recombinant immunotoxins.
      PubDate: 2018-04-10
      DOI: 10.1007/s11103-018-0726-9
       
  • Proteomic and physiological analyses reveal the role of exogenous
           spermidine on cucumber roots in response to Ca(NO 3 ) 2 stress
    • Authors: Jing Du; Shirong Guo; Jin Sun; Sheng Shu
      Abstract: Key message The mechanism of exogenous Spd-induced Ca(NO3)2 stress tolerance in cucumber was studied by proteomics and physiological analyses. Protein–protein interaction network revealed 13 key proteins involved in Spd-induced Ca(NO3)2 stress resistance. Ca(NO3)2 stress is one of the major reasons for secondary salinization that limits cucumber plant development in greenhouse. The conferred protective role of exogenous Spd on cucumber in response to Ca(NO3)2 stress cues involves changes at the cellular and physiological levels. To investigate the molecular foundation of exogenous Spd in Ca(NO3)2 stress tolerance, a proteomic approach was performed in our work. After a 9 days period of Ca(NO3)2 stress and/or exogenous Spd, 71 differential protein spots were confidently identified. The resulting proteins were enriched in seven different categories of biological processes, including protein metabolism, carbohydrate and energy metabolism, ROS homeostasis and stress defense, cell wall related, transcription, others and unknown. Protein metabolism (31.2%), carbohydrate and energy metabolism (15.6%), ROS homeostasis and stress defense (32.5%) were the three largest functional categories in cucumber root and most of them were significantly increased by exogenous Spd. The Spd-responsive protein interaction network revealed 13 key proteins, whose accumulation changes could be critical for Spd-induced resistance; all 13 proteins were upregulated by Spd at transcriptional and protein levels in response to Ca(NO3)2 stress. Furthermore, accumulation of antioxidant enzymes, non-enzymatic antioxidant and polyamines, along with reduction of H2O2 and MDA, were detected after exogenous Spd application during Ca(NO3)2 stress. The results of these proteomic and physiological analyses in cucumber root may facilitate a better understanding of the underlying mechanism of Ca(NO3)2 stress tolerance mediated by exogenous Spd.
      PubDate: 2018-04-09
      DOI: 10.1007/s11103-018-0721-1
       
  • Global gene regulation in tomato plant ( Solanum lycopersicum ) responding
           to vector ( Bactericera cockerelli ) feeding and pathogen (‘ Candidatus
           Liberibacter solanacearum’) infection
    • Authors: Ordom Brian Huot; Julien Gad Levy; Cecilia Tamborindeguy
      Abstract: Key message Different responses are elicited in tomato plants by Bactericera cockerelli harboring or not the pathogen ‘Candidatus Liberibacter solanacearum’. ‘Candidatus Liberibacter solanacearum’ (Lso) has emerged as a major pathogen of crops worldwide. This bacterial pathogen is transmitted by Bactericera cockerelli, the tomato psyllid, to solanaceous crops. In this study, the transcriptome profiles of tomato (Solanum lycopersicum) exposed to B. cockerelli infestation and Lso infection were evaluated at 1, 2 and 4 weeks following colonization and/or infection. The plant transcriptional responses to Lso-negative B. cockerelli were different than plant responses to Lso-positive B. cockerelli. The comparative transcriptome analyses of plant responses to Lso-negative B. cockerelli revealed the up-regulation of genes associated with plant defenses regardless of the time-point. In contrast, the general responses to Lso-positive B. cockerelli and Lso-infection were temporally different. Infected plants down-regulated defense genes at week one while delayed the up-regulation of the defense genes until weeks two and four, time points in which early signs of disease development were also detected in the transcriptional response. For example, infected plants regulated carbohydrate metabolism genes which could be linked to the disruption of sugar distribution usually associated with Lso infection. Also, infected plants down-regulated photosynthesis-related genes potentially resulting in plant chlorosis, another symptom associated with Lso infection. Overall, this study highlights that tomato plants induce different sets of genes in response to different stages of B. cockerelli infestation and Lso infection. This is the first transcriptome study of tomato responses to B. cockerelli and Lso, a first step in the direction of finding plant defense genes to enhance plant resistance.
      PubDate: 2018-04-04
      DOI: 10.1007/s11103-018-0724-y
       
  • Functionally redundant LNG3 and LNG4 genes regulate turgor-driven polar
           cell elongation through activation of XTH17 and XTH24
    • Authors: Young Koung Lee; Ji Ye Rhee; Seong Hee Lee; Gap Chae Chung; Soon Ju Park; Shoji Segami; Masayohi Maeshima; Giltsu Choi
      Abstract: Key message In this work, we genetically characterized the function of Arabidopsis thaliana, LONGIFOLIA (LNG1), LNG2, LNG3, LNG4, their contribution to regulate vegetative architecture in plant. We used molecular and biophysical approaches to elucidate a gene function that regulates vegetative architecture, as revealed by the leaf phenotype and later effects on flowering patterns in Arabidopsis loss-of-function mutants. As a result, LNG genes play an important role in polar cell elongation by turgor pressure controlling the activation of XTH17 and XTH24. Plant vegetative architecture is related to important traits that later influence the floral architecture involved in seed production. Leaf morphology is the primary key trait to compose plant vegetative architecture. However, molecular mechanism on leaf shape determination is not fully understood even in the model plant A. thaliana. We previously showed that LONGIFOLIA (LNG1) and LONGIFOLIA2 (LNG2) genes regulate leaf morphology by promoting longitudinal cell elongation in Arabidopsis. In this study, we further characterized two homologs of LNG1, LNG3, and LNG4, using genetic, biophysical, and molecular approaches. Single loss-of-function mutants, lng3 and lng4, do not show any phenotypic difference, but mutants of lng quadruple (lngq), and lng1/2/3 and lng1/2/4 triples, display reduced leaf length, compared to wild type. Using the paradermal analysis, we conclude that the reduced leaf size of lngq is due to decreased cell elongation in the direction of longitudinal leaf growth, and not decreased cell proliferation. This data indicate that LNG1/2/3/4 are functionally redundant, and are involved in polar cell elongation in Arabidopsis leaf. Using a biophysical approach, we show that the LNGs contribute to maintain high turgor pressure, thus regulating turgor pressure-dependent polar cell elongation. In addition, gene expression analysis showed that LNGs positively regulate the expression of the cell wall modifying enzyme encoded by a multi-gene family, xyloglucan endotransglucosylase/hydrolase (XTH). Taking all of these together, we propose that LNG related genes play an important role in polar cell elongation by changing turgor pressure and controlling the activation of XTH17 and XTH24.
      PubDate: 2018-04-03
      DOI: 10.1007/s11103-018-0722-0
       
  • A tandem array of UDP-glycosyltransferases from the UGT73C subfamily
           glycosylate sapogenins, forming a spectrum of mono- and bisdesmosidic
           saponins
    • Authors: Pernille Østerbye Erthmann; Niels Agerbirk; Søren Bak
      Abstract: Key message This study identifies six UGT73Cs all able to glucosylate sapogenins at positions 3 and/or 28 which demonstrates that B. vulgaris has a much richer arsenal of UGTs involved in saponin biosynthesis than initially anticipated. The wild cruciferous plant Barbarea vulgaris is resistant to some insects due to accumulation of two monodesmosidic triterpenoid saponins, oleanolic acid 3-O-β-cellobioside and hederagenin 3-O-β-cellobioside. Insect resistance depends on the structure of the sapogenin aglycone and the glycosylation pattern. The B. vulgaris saponin profile is complex with at least 49 saponin-like metabolites, derived from eight sapogenins and including up to five monosaccharide units. Two B. vulgaris UDP-glycosyltransferases, UGT73C11 and UGT73C13, O-glucosylate sapogenins at positions 3 and 28, forming mainly 3-O-β-d-glucosides. The aim of this study was to identify UGTs responsible for the diverse saponin oligoglycoside moieties observed in B. vulgaris. Twenty UGT genes from the insect resistant genotype were selected and heterologously expressed in Nicotiana benthamiana and/or Escherichia coli. The extracts were screened for their ability to glycosylate sapogenins (oleanolic acid, hederagenin), the hormone 24-epibrassinolide and sapogenin monoglucosides (hederagenin and oleanolic acid 3-O-β-d-glucosides). Six UGTs from the UGT73C subfamily were able to glucosylate both sapogenins and both monoglucosides at positions 3 and/or 28. Some UGTs formed bisdesmosidic saponins efficiently. At least four UGT73C genes were localized in a tandem array with UGT73C11 and possibly UGT73C13. This organization most likely reflects duplication events followed by sub- and neofunctionalization. Indeed, signs of positive selection on several amino acid sites were identified and modelled to be localized on the UGT protein surface. This tandem array is proposed to initiate higher order bisdesmosidic glycosylation of B. vulgaris saponins, leading to the recently discovered saponin structural diversity, however, not directly to known cellobiosidic saponins.
      PubDate: 2018-03-30
      DOI: 10.1007/s11103-018-0723-z
       
  • BPH1, a novel substrate receptor of CRL3, plays a repressive role in ABA
           signal transduction
    • Authors: Og-Geum Woo; Soon-Hee Kim; Seok Keun Cho; Sang-Hoon Kim; Han Nim Lee; Taijoon Chung; Seong Wook Yang; Jae-Hoon Lee
      Abstract: Key message BPH1 acts as a substrate receptor of CRL3 complex and negatively regulates ABA-mediated cellular responses. The study on its function provides information that helps further understand the relationship between ABA signaling and UPS. Abscisic acid (ABA) plays a crucial role in a variety of cellular processes, including seed dormancy, inhibition of seedling growth, and drought resistance in plants. Cullin3-RING E3 ligase (CRL3) complex is a type of multi-subunit E3 ligase, and BTB/POZ protein, a component of CRL3 complex, functions as a receptor to determine a specific substrate. To elucidate the CRL3 complex that participates in ABA-mediated cellular processes, we first investigated ABA-inducible BTB/POZ genes based on data from the AtGenExpress Visualization Tool (AVT). We then isolated an ABA-inducible gene encoding a potential CRL3 substrate receptor in Arabidopsis, BPH1 (BTB/POZ protein hypersensitive to ABA 1). The isolate gene has a BTB/POZ domain and a NPH3 domain within its N-terminal and C-terminal region, respectively. Yeast two-hybrid and co-immunoprecipitation assays showed that BPH1 physically interacted with cullin3a, a scaffold protein of CRL3, suggesting that it functions as an Arabidopsis CRL3 substrate receptor. The functional mutation of BPH1 caused delayed seed germination in response to ABA and enhanced sensitivity by NaCl and mannitol treatments as ABA-related stresses. Moreover, bph1 mutants exhibited enhanced stomatal closure under ABA application and reduced water loss when compared with wild-type, implying their enhanced tolerance to drought stress. Based on the information from microarray/AVT data and expression analysis of various ABA-inducible genes between wild-type and bph1 plants following ABA treatments, we concluded loss of BPH1 resulted in hyper-induction of a large portion of ABA-inducible genes in response to ABA. Taken together, these results show that BPH1 is negatively involved in ABA-mediated cellular events.
      PubDate: 2018-03-21
      DOI: 10.1007/s11103-018-0717-x
       
  • The wheat TabZIP2 transcription factor is activated by the nutrient
           starvation-responsive SnRK3/CIPK protein kinase
    • Authors: Sukanya Luang; Pradeep Sornaraj; Natalia Bazanova; Wei Jia; Omid Eini; Syed Sarfraz Hussain; Nataliya Kovalchuk; Pradeep K. Agarwal; Maria Hrmova; Sergiy Lopato
      Abstract: Key message The understanding of roles of bZIP factors in biological processes during plant development and under abiotic stresses requires the detailed mechanistic knowledge of behaviour of TFs. Basic leucine zipper (bZIP) transcription factors (TFs) play key roles in the regulation of grain development and plant responses to abiotic stresses. We investigated the role and molecular mechanisms of function of the TabZIP2 gene isolated from drought-stressed wheat plants. Molecular characterisation of TabZIP2 and derived protein included analyses of gene expression and its target promoter, and the influence of interacting partners on the target promoter activation. Two interacting partners of TabZIP2, the 14-3-3 protein, TaWIN1 and the bZIP transcription factor TaABI5L, were identified in a Y2H screen. We established that under elevated ABA levels the activity of TabZIP2 was negatively regulated by the TaWIN1 protein and positively regulated by the SnRK3/CIPK protein kinase WPK4, reported previously to be responsive to nutrient starvation. The physical interaction between the TaWIN1 and the WPK4 was detected. We also compared the influence of homo- and hetero-dimerisation of TabZIP2 and TaABI5L on DNA binding. TabZIP2 gene functional analyses were performed using drought-inducible overexpression of TabZIP2 in transgenic wheat. Transgenic plants grown under moderate drought during flowering, were smaller than control plants, and had fewer spikes and seeds per plant. However, a single seed weight was increased compared to single seed weights of control plants in three of four evaluated transgenic lines. The observed phenotypes of transgenic plants and the regulation of TabZIP2 activity by nutrient starvation-responsive WPK4, suggest that the TabZIP2 could be the part of a signalling pathway, which controls the rearrangement of carbohydrate and nutrient flows in plant organs in response to drought.
      PubDate: 2018-03-21
      DOI: 10.1007/s11103-018-0713-1
       
  • Analysis of the DNA methylation patterns and transcriptional regulation of
           the NB-LRR-encoding gene family in Arabidopsis thaliana
    • Authors: Weiwen Kong; Bin Li; Qianqian Wang; Bin Wang; Xiaoke Duan; Li Ding; Yanke Lu; Li-Wei Liu; Honggui La
      Abstract: Key message The relationships between transcription and methylation were revealed in Arabidopsis thaliana NB-LRR-encoding genes in wild type (Col-0) and different mutants. Plant nucleotide-binding, leucine-rich repeat (NB-LRR) proteins constitute a large family that plays predominant roles in disease resistance. However, the regulation of NB-LRR-encoding genes at the transcriptional level is still poorly understood. Recently, DNA cytosine methylation in eukaryotes has been described as serving an important function in regulating gene expression. Here, we analysed the DNA methylation patterns of NB-LRR-encoding genes in Arabidopsis thaliana in samples from a wild type (Col-0) and ago4, met1, cmt3, drm1/2, and ddm1 mutants. Our results revealed that the vast majority of the NB-LRR-encoding genes in Col-0 were methylated, and the DNA methylation occurred predominantly in the CG sequence context. Moreover, DNA methylation was widely distributed in both the promoters and the bodies of most NB-LRR-encoding genes. Our results also showed that the loss of AGO4, MET1, CMT3, DRM1/2 or DDM1 functions generally led to decreased cytosine methylation in the NB-LRR-encoding genes. Analysis of the available transcriptome data from the wild type and the met1, cmt3, drm1/2 and ddm1 mutants revealed that differences in the transcription levels between the wild type and mutants were statistically significant for 63 of the NB-LRR-encoding genes. Of these genes, 38 were significantly upregulated, and the other 25 were significantly downregulated. Some NB-LRR-encoding genes with differential expression levels, which were revealed by the mRNA-Seq data, were confirmed to be significantly upregulated or downregulated in the mutants compared to the wild type by using quantitative RT-PCR. These data suggest that some Arabidopsis NB-LRR-encoding genes are likely to be regulated by altered DNA methylation patterns.
      PubDate: 2018-03-10
      DOI: 10.1007/s11103-018-0715-z
       
 
 
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