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Journal Cover Plant Molecular Biology
  [SJR: 1.842]   [H-I: 121]   [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  [2281 journals]
  • Comparative analysis of the pteridophyte Adiantum MFT ortholog reveals the
           specificity of combined FT/MFT C and N terminal interaction with FD for
           the regulation of the downstream gene AP1
    • Abstract: Abstract To study the evolution of phosphatidylethanolamine-binding protein (PEBP) gene families in non-flowering plants, we performed a functional analysis of the PEBP gene AcMFT of the MFT clade in the pteridophyte Adiantum capillus-veneris. The expression of AcMFT was regulated by photoperiod similar to that for FT under both long day and short day conditions. Ectopic expression of AcMFT in Arabidopsis promotes the floral transition and partially complements the late flowering defect in transgenic Arabidopsis ft-1 mutants, suggesting that AcMFT functions similarly to FT in flowering plants. Interestingly, a similar partial compensation of the ft-1 late flowering phenotype was observed in Arabidopsis ectopically expressing only exon 4 of the C terminus of AcMFT and FT. This result indicated that the fourth exon of AcMFT and FT plays a similar and important role in promoting flowering. Further analysis indicated that exons 1–3 in the N terminus specifically enhanced the function of FT exon 4 in controlling flowering in Arabidopsis. Protein pull-down assays indicated that Arabidopsis FD proteins interact with full-length FT and AcMFT, as well as peptides encoded by 1–3 exon fragments or the 4th exon alone. Furthermore, similar FRET efficiencies for FT-FD and AcMFT-FD heterodimer in nucleus were observed. These results indicated that FD could form the similar complex with FT and AcMFT. Further analysis indicated that the expression of AP1, a gene downstream of FT, was up-regulated more strongly by FT than AcMFT in transgenic Arabidopsis. Our results revealed that AcMFT from a non-flowering plant could interact with FD to regulate the floral transition and that this function was reduced due to the weakened ability of AcMFT-FD to activate the downstream gene AP1.
      PubDate: 2016-05-23
       
  • Allantoin accumulation mediated by allantoinase downregulation and
           transport by Ureide Permease 5 confers salt stress tolerance to
           Arabidopsis plants
    • Abstract: Abstract Allantoin, a metabolite generated in the purine degradation pathway, was primarily considered an intermediate for recycling of the abundant nitrogen assimilated in plant purines. More specifically, tropical legumes utilize allantoin and allantoic acid as major nodule-to-shoot nitrogen transport compounds. In other species, an increase in allantoin content was observed under different stress conditions, but the underlying molecular mechanisms remain poorly understood. In this work, Arabidopsis thaliana was used as a model system to investigate the effects of salt stress on allantoin metabolism and to know whether its accumulation results in plant protection. Plant seedlings treated with NaCl at different concentrations showed higher allantoin and lower allantoic acid contents. Treatments with NaCl favored the expression of genes involved in allantoin synthesis, but strongly repressed the unique gene encoding allantoinase (AtALN). Due to the potential regulatory role of this gene for allantoin accumulation, AtALN promoter activity was studied using a reporter system. GUS mediated coloration was found in specific plant tissues and was diminished with increasing salt concentrations. Phenotypic analysis of knockout, knockdown and stress-inducible mutants for AtALN revealed that allantoin accumulation is essential for salt stress tolerance. In addition, the possible role of allantoin transport was investigated. The Ureide Permease 5 (UPS5) is expressed in the cortex and endodermis of roots and its transcription is enhanced by salt treatment. Ups5 knockout plants under salt stress presented a susceptible phenotype and altered allantoin root-to-shoot content ratios. Possible roles of allantoin as a protectant compound in oxidative events or signaling are discussed.
      PubDate: 2016-05-21
       
  • Reduced function of the RNA-binding protein FPA rescues a T-DNA insertion
           mutant in the Arabidopsis ZHOUPI gene by promoting transcriptional
           read-through
    • Abstract: Abstract T-DNA insertion mutants have been widely used to investigate plant gene functions. Unexpectedly, in several reported cases, the phenotype of T-DNA insertion mutations can be suppressed because of trans T-DNA interactions associated with epigenetic modification, which indicates that caution is needed when T-DNA mutants are used. In the present study, we characterized a novel process suppressing a T-DNA mutation. The spz2 (suppressor of zou 2) mutant was isolated as a suppressor of the phenotype of the zou-4 mutant caused by a T-DNA insertion in the first intron. The spz2 mutation partially recovered the native ZOU gene expression in the zou-4 background, but not in two other zou alleles, zou-2 and zou-3, with T-DNAs inserted in the exon and intron, respectively. The suppressed phenotype was inherited in a Mendelian fashion and is not associated with epigenetic modification. The recovery of the native ZOU gene expression in the spz2 zou-4 double mutant is caused by transcriptional read-through of the intronic T-DNA as a result of decreased proximal polyadenylation. SPZ2 encodes an RNA-binding protein, FPA, which is known to regulate polyadenylation site selection. This is the first example of FPA rescuing a T-DNA insertion mutation by affecting the polyadenylation site selection.
      PubDate: 2016-05-10
       
  • Jasmonate signaling is activated in the very early stages of iron
           deficiency responses in rice roots
    • Abstract: Abstract Under low iron availability, plants induce the expression of various genes involved in iron uptake and translocation at the transcriptional level. This iron deficiency response is affected by various plant hormones, but the roles of jasmonates in this response are not well-known. We investigated the involvement of jasmonates in rice iron deficiency responses. High rates of jasmonate-inducible genes were induced during the very early stages of iron deficiency treatment in rice roots. Many jasmonate-inducible genes were also negatively regulated by the ubiquitin ligases OsHRZ1 and OsHRZ2 and positively regulated by the transcription factor IDEF1. Ten out of 35 genes involved in jasmonate biosynthesis and signaling were rapidly induced at 3 h of iron deficiency treatment, and this induction preceded that of known iron deficiency-inducible genes involved in iron uptake and translocation. Twelve genes involved in jasmonate biosynthesis and signaling were also upregulated in HRZ-knockdown roots. Endogenous concentrations of jasmonic acid and jasmonoyl isoleucine tended to be rapidly increased in roots in response to iron deficiency treatment, whereas these concentrations were higher in HRZ-knockdown roots under iron-sufficient conditions. Analysis of the jasmonate-deficient cpm2 mutant revealed that jasmonates repress the expression of many iron deficiency-inducible genes involved in iron uptake and translocation under iron sufficiency, but this repression is partly canceled under an early stage of iron deficiency. These results indicate that jasmonate signaling is activated during the very early stages of iron deficiency, which is partly regulated by IDEF1 and OsHRZs.
      PubDate: 2016-05-03
       
  • Arabidopsis thaliana gonidialess A/Zuotin related factors (GlsA/ZRF) are
           essential for maintenance of meristem integrity
    • Abstract: Abstract Observation of a differential expression pattern, including strong expression in meristematic tissue of an Agave tequilana GlsA/ZRF ortholog suggested an important role for this gene during bulbil formation and developmental changes in this species. In order to better understand this role, the two GlsA/ZFR orthologs present in the genome of Arabidopsis thaliana were functionally characterized by analyzing expression patterns, double mutant phenotypes, promoter-GUS fusions and expression of hormone related or meristem marker genes. Patterns of expression for A. thaliana show that GlsA/ZFR genes are strongly expressed in SAMs and RAMs in mature plants and developing embryos and double mutants showed multiple changes in morphology related to both SAM and RAM tissues. Typical double mutants showed stunted growth of aerial and root tissue, formation of multiple ectopic meristems and effects on cotyledons, leaves and flowers. The KNOX genes STM and BP were overexpressed in double mutants whereas CLV3, WUSCHEL and AS1 were repressed and lack of AtGlsA expression was also associated with changes in localization of auxin and cytokinin. These results suggest that GlsA/ZFR is an essential component of the machinery that maintains the integrity of SAM and RAM tissue and underline the potential to identify new genes or gene functions based on observations in non-model plants.
      PubDate: 2016-05-01
       
  • Co-expression network analysis reveals transcription factors associated to
           cell wall biosynthesis in sugarcane
    • Abstract: Abstract Sugarcane is a hybrid of Saccharum officinarum and Saccharum spontaneum, with minor contributions from other species in Saccharum and other genera. Understanding the molecular basis of cell wall metabolism in sugarcane may allow for rational changes in fiber quality and content when designing new energy crops. This work describes a comparative expression profiling of sugarcane ancestral genotypes: S. officinarum, S. spontaneum and S. robustum and a commercial hybrid: RB867515, linking gene expression to phenotypes to identify genes for sugarcane improvement. Oligoarray experiments of leaves, immature and intermediate internodes, detected 12,621 sense and 995 antisense transcripts. Amino acid metabolism was particularly evident among pathways showing natural antisense transcripts expression. For all tissues sampled, expression analysis revealed 831, 674 and 648 differentially expressed genes in S. officinarum, S. robustum and S. spontaneum, respectively, using RB867515 as reference. Expression of sugar transporters might explain sucrose differences among genotypes, but an unexpected differential expression of histones were also identified between high and low Brix° genotypes. Lignin biosynthetic genes and bioenergetics-related genes were up-regulated in the high lignin genotype, suggesting that these genes are important for S. spontaneum to allocate carbon to lignin, while S. officinarum allocates it to sucrose storage. Co-expression network analysis identified 18 transcription factors possibly related to cell wall biosynthesis while in silico analysis detected cis-elements involved in cell wall biosynthesis in their promoters. Our results provide information to elucidate regulatory networks underlying traits of interest that will allow the improvement of sugarcane for biofuel and chemicals production.
      PubDate: 2016-05-01
       
  • The peach HECATE3 -like gene FLESHY plays a double role during fruit
           development
    • Abstract: Abstract Tight control of cell/tissue identity is essential for a correct and functional organ patterning, an important component of overall fruit development and eventual maturation and ripening. Despite many investigations regarding the molecular determinants of cell identity in fruits of different species, a useful model able to depict the regulatory networks governing this relevant part of fruit development is still missing. Here we described the peach fruit as a system to link the phenotype of a slow ripening (SR) selection to an altered transcriptional regulation of genes involved in determination of mesocarp cell identity providing insight toward molecular regulation of fruit tissue formation. Morpho-anatomical observations and metabolomics analyses performed during fruit development on the reference cultivar Fantasia, compared to SR, revealed that the mesocarp of SR maintained typical immaturity traits (e.g. small cell size, high amino acid contents and reduced sucrose) throughout development, along with a strong alteration of phenylpropanoid contents, resulting in accumulation of phenylalanine and lignin. These findings suggest that the SR mesocarp is phenotypically similar to a lignifying endocarp. To test this hypothesis, the expression of genes putatively involved in determination of drupe tissues identity was assessed. Among these, the peach HEC3-like gene FLESHY showed a strongly altered expression profile consistent with pit hardening and fruit ripening, generated at a post-transcriptional level. A double function for FLESHY in channelling the phenylpropanoid pathway to either lignin or flavour/aroma is suggested, along with its possible role in triggering auxin-ethylene cross talk at the start of ripening.
      PubDate: 2016-05-01
       
  • Transcriptome comparisons shed light on the pre-condition and potential
           barrier for C 4 photosynthesis evolution in eudicots
    • Abstract: Abstract C4 photosynthesis evolved independently from C3 photosynthesis in more than 60 lineages. Most of the C4 lineages are clustered together in the order Poales and the order Caryophyllales while many other angiosperm orders do not have C4 species, suggesting the existence of biological pre-conditions in the ancestral C3 species that facilitate the evolution of C4 photosynthesis in these lineages. To explore pre-adaptations for C4 photosynthesis evolution, we classified C4 lineages into the C4-poor and the C4-rich groups based on the percentage of C4 species in different genera and conducted a comprehensive comparison on the transcriptomic changes between the non-C4 species from the C4-poor and the C4-rich groups. Results show that species in the C4-rich group showed higher expression of genes related to oxidoreductase activity, light reaction components, terpene synthesis, secondary cell synthesis, C4 cycle related genes and genes related to nucleotide metabolism and senescence. In contrast, C4-poor group showed up-regulation of a PEP/Pi translocator, genes related to signaling pathway, stress response, defense response and plant hormone metabolism (ethylene and brassinosteroid). The implications of these transcriptomic differences between the C4-rich and C4-poor groups to C4 evolution are discussed.
      PubDate: 2016-05-01
       
  • Expression of grapevine AINTEGUMENTA -like genes is associated with
           variation in ovary and berry size
    • Abstract: Abstract Fruit size is a highly important trait for most fruit and vegetable crops. This trait has been a main selection target and could be involved in divergent selection processes leading to the differentiation between modern table and wine cultivars. Even though its determination is highly influenced by cultural practices, several regions within the grapevine genome have been identified affecting berry size, either directly or indirectly through their effect on seed content. Using grapevine seeded cultivars, we have analyzed the relationship between ovary cell number and the final size of ovaries and berry fruits. We also performed the characterization of the grapevine AINTEGUMENTA-LIKE family, since it is well reported in Arabidopsis that AINTEGUMENTA (ANT) regulates cell proliferation and organ growth in flower organ primordia by maintaining the meristematic competence of cells during organogenesis. Here we show that orthologous grapevine gene expression associate with flower developmental stages suggesting a similar biological role for this gene family in this species. Moreover, we detected a correlation between those organs size and the level of expression of VviANT1 the grapevine homolog of AtANT. This grapevine gene also co-localizes in linkage group 18 with the confidence interval of a previously detected QTL for berry size. Thus our results suggest the involvement of ANT in the regulation of berry size in grapevine.
      PubDate: 2016-05-01
       
  • Evolutionary origin of Rosaceae-specific active non-autonomous hAT
           elements and their contribution to gene regulation and genomic structural
           variation
    • Abstract: Abstract Transposable elements account for approximately 30 % of the Prunus genome; however, their evolutionary origin and functionality remain largely unclear. In this study, we identified a hAT transposon family, termed Moshan, in Prunus. The Moshan elements consist of three types, aMoshan, tMoshan, and mMoshan. The aMoshan and tMoshan types contain intact or truncated transposase genes, respectively, while the mMoshan type is miniature inverted-repeat transposable element (MITE). The Moshan transposons are unique to Rosaceae, and the copy numbers of different Moshan types are significantly correlated. Sequence homology analysis reveals that the mMoshan MITEs are direct deletion derivatives of the tMoshan progenitors, and one kind of mMoshan containing a MuDR-derived fragment were amplified predominately in the peach genome. The mMoshan sequences contain cis-regulatory elements that can enhance gene expression up to 100-fold. The mMoshan MITEs can serve as potential sources of micro and long noncoding RNAs. Whole-genome re-sequencing analysis indicates that mMoshan elements are highly active, and an insertion into S-haplotype-specific F-box gene was reported to cause the breakdown of self-incompatibility in sour cherry. Taken together, all these results suggest that the mMoshan elements play important roles in regulating gene expression and driving genomic structural variation in Prunus.
      PubDate: 2016-05-01
       
  • Rice OsVAMP714, a membrane-trafficking protein localized to the
           chloroplast and vacuolar membrane, is involved in resistance to rice blast
           disease
    • Abstract: Abstract Membrane trafficking plays pivotal roles in many cellular processes including plant immunity. Here, we report the characterization of OsVAMP714, an intracellular SNARE protein, focusing on its role in resistance to rice blast disease caused by the fungal pathogen Magnaporthe oryzae. Disease resistance tests using OsVAMP714 knockdown and overexpressing rice plants demonstrated the involvement of OsVAMP714 in blast resistance. The overexpression of OsVAMP7111, whose product is highly homologous to OsVAMP714, did not enhance blast resistance to rice, implying a potential specificity of OsVAMP714 to blast resistance. OsVAMP714 was localized to the chloroplast in mesophyll cells and to the cellular periphery in epidermal cells of transgenic rice plant leaves. We showed that chloroplast localization is critical for the normal OsVAMP714 functioning in blast resistance by analyzing the rice plants overexpressing OsVAMP714 mutants whose products did not localize in the chloroplast. We also found that OsVAMP714 was located in the vacuolar membrane surrounding the invasive hyphae of M. oryzae. Furthermore, we showed that OsVAMP714 overexpression promotes leaf sheath elongation and that the first 19 amino acids, which are highly conserved between animal and plant VAMP7 proteins, are crucial for normal rice plant growths. Our studies imply that the OsVAMP714-mediated trafficking pathway plays an important role in rice blast resistance as well as in the vegetative growth of rice.
      PubDate: 2016-05-01
       
  • Identification and functional characterization of the pepper CaDRT1 gene
           involved in the ABA-mediated drought stress response
    • Abstract: Abstract Plants are constantly challenged by various environmental stresses, including high salinity and drought, and they have evolved defense mechanisms to counteract the deleterious effects of these stresses. The plant hormone abscisic acid (ABA) regulates plant growth and developmental processes and mediates abiotic stress responses. Here, we identified the Capsicum annuum DRought Tolerance 1 (CaDRT1) gene from pepper leaves treated with ABA. CaDRT1 was strongly expressed in pepper leaves in response to environmental stresses and after ABA treatment, suggesting that the CaDRT1 protein functions in the abiotic stress response. Knockdown expression of CaDRT1 via virus-induced gene silencing resulted in a high level of drought susceptibility, and this was characterized by increased transpirational water loss via decreased stomatal closure. CaDRT1-overexpressing (OX) Arabidopsis plants exhibited an ABA-hypersensitive phenotype during the germinative, seedling, and adult stages. Additionally, these CaDRT1-OX plants exhibited a drought-tolerant phenotype characterized by low levels of transpirational water loss, high leaf temperatures, increased stomatal closure, and enhanced expression levels of drought-responsive genes. Taken together, our results suggest that CaDRT1 is a positive regulator of the ABA-mediated drought stress response.
      PubDate: 2016-05-01
       
  • A temperature-sensitive allele of a putative mRNA splicing helicase
           down-regulates many cell wall genes and causes radial swelling in
           Arabidopsis thaliana
    • Abstract: Abstract The putative RNA helicase encoded by the Arabidopsis gene At1g32490 is a homolog of the yeast splicing RNA helicases Prp2 and Prp22. We isolated a temperature-sensitive allele (rsw12) of the gene in a screen for root radial swelling mutants. Plants containing this allele grown at the restrictive temperature showed weak radial swelling, were stunted with reduced root elongation, and contained reduced levels of cellulose. The role of the protein was further explored by microarray analysis. By using both fold change cutoffs and a weighted gene coexpression network analysis (WGCNA) to investigate coexpression of genes, we found that the radial swelling phenotype was not linked to genes usually associated with primary cell wall biosynthesis. Instead, the mutation has strong effects on expression of secondary cell wall related genes. Many genes potentially associated with secondary walls were present in the most significant WGCNA module, as were genes coding for arabinogalactans and proteins with GPI anchors. The proportion of up-regulated genes that possess introns in rsw12 was above that expected if splicing was unrelated to the activity of the RNA helicase, suggesting that the helicase does indeed play a role in splicing in Arabidopsis. The phenotype may be due to a change in the expression of one or more genes coding for cell wall proteins.
      PubDate: 2016-05-01
       
  • Evolutionary history of double-stranded RNA binding proteins in plants:
           identification of new cofactors involved in easiRNA biogenesis
    • Abstract: Abstract In this work, we retrace the evolutionary history of plant double-stranded RNA binding proteins (DRBs), a group of non-catalytic factors containing one or more double-stranded RNA binding motif (dsRBM) that play important roles in small RNA biogenesis and functions. Using a phylogenetic approach, we show that multiple dsRBM DRBs are systematically composed of two different types of dsRBMs evolving under different constraints and likely fulfilling complementary functions. In vascular plants, four distinct clades of multiple dsRBM DRBs are always present with the exception of Brassicaceae species, that do not possess member of the newly identified clade we named DRB6. We also identified a second new and highly conserved DRB family (we named DRB7) whose members possess a single dsRBM that shows concerted evolution with the most C-terminal dsRBM domain of the Dicer-like 4 (DCL4) proteins. Using a BiFC approach, we observed that Arabidopsis thaliana DRB7.2 (AtDRB7.2) can directly interact with AtDRB4 but not with AtDCL4 and we provide evidence that both AtDRB7.2 and AtDRB4 participate in the epigenetically activated siRNAs pathway.
      PubDate: 2016-05-01
       
  • A residue substitution in the plastid ribosomal protein L12/AL1 produces
           defective plastid ribosome and causes early seedling lethality in rice
    • Abstract: Abstract The plastid ribosome is essential for chloroplast biogenesis as well as seedling formation. As the plastid ribosome closely resembles the prokaryotic 70S ribosome, many plastid ribosomal proteins (PRPs) have been identified in higher plants. However, their assembly in the chloroplast ribosome in rice remains unclear. In the present study, we identified a novel rice mutant, albino lethal 1 (al1), from a chromosome segment substitution line population. The al1 mutant displayed an albino phenotype at the seedling stage and did not survive past the three-leaf stage. No other apparent differences in plant morphology were observed in the al1 mutant. The albino phenotype of the al1 mutant was associated with decreased chlorophyll content and abnormal chloroplast morphology. Using fine mapping, AL1 was shown to encode the PRPL12, a protein localized in the chloroplasts of rice, and a spontaneous single-nucleotide mutation (C/T), resulting in a residue substitution from leucine in AL1 to phenylalanine in al1, was found to be responsible for the early seedling lethality. This point mutation is located at the L10 interface feature of the L12/AL1 protein. Yeast two-hybrid analysis showed that there was no physical interaction between al1 and PRPL10. In addition, the mutation had little effect on the transcript abundance of al1, but had a remarkable effect on the protein abundance of al1 and transcript abundance of chloroplast biogenesis-related and photosynthesis-related genes. These results provide a first glimpse into the molecular details of L12’s function in rice.
      PubDate: 2016-05-01
       
  • A wheat superoxide dismutase gene TaSOD2 enhances salt resistance through
           modulating redox homeostasis by promoting NADPH oxidase activity
    • Abstract: Abstract Superoxide dismutase (SOD) is believed to enhance abiotic stress resistance by converting superoxide radical (O2 −) to H2O2 to lower ROS level and maintain redox homeostasis. ROS level is controlled via biphasic machinery of ROS production and scavenging. However, whether the role of SOD in abiotic stress resistance is achieved through influencing the biophasic machinery is not well documented. Here, we identified a wheat copper-zinc (Cu/Zn) SOD gene, TaSOD2, who was responsive to NaCl and H2O2. TaSOD2 overexpression in wheat and Arabidopsis elevated SOD activities, and enhanced the resistance to salt and oxidative stress. TaSOD2 overexpression reduced H2O2 level but accelerated O2 − accumulation. Further, it improved the activities of H2O2 metabolic enzymes, elevated the activity of O2 − producer NADPH oxidase (NOX), and promoted the transcription of NOX encoding genes. The inhibition of NOX activity and the mutation of NOX encoding genes both abolished the salt resistance of TaSOD2 overexpression lines. These data indicate that Cu/Zn SOD enhances salt resistance, which is accomplished through modulating redox homeostasis via promoting NOX activity.
      PubDate: 2016-05-01
       
  • WRKY1 regulates stomatal movement in drought-stressed Arabidopsis thaliana
    • Abstract: Abstract A key response of plants to moisture stress is stomatal closure, a process mediated by the phytohormone abscisic acid (ABA). Closure is affected by changes in the turgor of the stomatal guard cell. The transcription factor WRKY1 is a part of the regulatory machinery underlying stomatal movements, and through this, in the plant’s response to drought stress. The loss-of-function T-DNA insertion mutant wrky1 was particularly sensitive to ABA, with respect to both ion channel regulation and stomatal movements, and less sensitive to drought than the wild type. Complementation of the wrky1 mutant resulted in the recovery of the wild type phenotype. The WRKY1 product localized to the nucleus, and was shown able to bind to the W-box domain in the promoters of MYB2, ABCG40, DREB1A and ABI5, and thereby to control their transcription in response to drought stress or ABA treatment. WRKY1 is thought to act as a negative regulator in guard cell ABA signalling.
      PubDate: 2016-05-01
       
  • Genome-wide identification and homeolog-specific expression analysis of
           the SnRK2 genes in Brassica napus guard cells
    • Abstract: Abstract Sucrose non-fermenting-1-related protein kinase 2 (SnRK2) proteins constitute a small plant-specific serine/threonine kinase family involved in abscisic acid (ABA) signaling and plant responses to biotic and abiotic stresses. Although SnRK2s have been well-studied in Arabidopsis thaliana, little is known about SnRK2s in Brassica napus. Here we identified 30 putative sequences encoding 10 SnRK2 proteins in the B. napus genome and the expression profiles of a subset of 14 SnRK2 genes in guard cells of B. napus. In agreement with its polyploid origin, B. napus maintains both homeologs from its diploid parents. The results of quantitative real-time PCR (qRT-PCR) and reanalysis of RNA-Seq data showed that certain BnSnRK2 genes were commonly expressed in leaf tissues in different varieties of B. napus. In particular, qRT-PCR results showed that 12 of the 14 BnSnRK2s responded to drought stress in leaves and in ABA-treated guard cells. Among them, BnSnRK2.4 and BnSnRK2.6 were of interest because of their robust responsiveness to ABA treatment and drought stress. Notably, BnSnRK2 genes exhibited up-regulation of different homeologs, particularly in response to abiotic stress. The homeolog expression bias in BnSnRK2 genes suggests that parental origin of genes might be responsible for efficient regulation of stress responses in polyploids. This work has laid a foundation for future functional characterization of the different BnSnKR2 homeologs in B. napus and its parents, especially their functions in guard cell signaling and stress responses.
      PubDate: 2016-05-01
       
  • TOMATO AGAMOUS1 and ARLEQUIN/TOMATO AGAMOUS - LIKE1 MADS-box genes have
           redundant and divergent functions required for tomato reproductive
           development
    • Abstract: Abstract Within the tomato MADS-box gene family, TOMATO AGAMOUS1 (TAG1) and ARLEQUIN/TOMATO AGAMOUS LIKE1 (hereafter referred to as TAGL1) are, respectively, members of the euAG and PLE lineages of the AGAMOUS clade. They perform crucial functions specifying stamen and carpel development in the flower and controlling late fruit development. To gain insight into the roles of TAG1 and TAGL1 genes and to better understand their functional redundancy and diversification, we characterized single and double RNAi silencing lines of these genes and analyzed expression profiles of regulatory genes involved in reproductive development. Double RNAi lines did show cell abnormalities in stamens and carpels and produced extremely small fruit-like organs displaying some sepaloid features. Expression analyses indicated that TAG1 and TAGL1 act together to repress fourth whorl sepal development, most likely through the MACROCALYX gene. Results also proved that TAG1 and TAGL1 have diversified their functions in fruit development: while TAG1 controls placenta and seed formation, TAGL1 participates in cuticle development and lignin biosynthesis inhibition. It is noteworthy that both TAG1 and double RNAi plants lacked seed development due to abnormalities in pollen formation. This seedless phenotype was not associated with changes in the expression of B-class stamen identity genes Tomato MADS-box 6 and Tomato PISTILLATA observed in silencing lines, suggesting that other regulatory factors should participate in pollen formation. Taken together, results here reported support the idea that both redundant and divergent functions of TAG1 and TAGL1 genes are needed to control tomato reproductive development.
      PubDate: 2016-04-28
       
  • Production of dengue virus envelope protein domain III-based antigens in
           tobacco chloroplasts using inducible and constitutive expression systems
    • Abstract: Abstract Dengue fever is a disease in many parts of the tropics and subtropics and about half the world’s population is at risk of infection according to the World Health Organization. Dengue is caused by any of the four related dengue virus serotypes DEN-1, -2, -3 and -4, which are transmitted to people by Aedes aegypti mosquitoes. Currently there is only one vaccine (Dengvaxia®) available (limited to a few countries) on the market since 2015 after half a century’s intensive efforts. Affordable and accessible vaccines against dengue are hence still urgently needed. The dengue envelop protein domain III (EDIII), which is capable of eliciting serotype-specific neutralizing antibodies, has become the focus for subunit vaccine development. To contribute to the development of an accessible and affordable dengue vaccine, in the current study we have used plant-based vaccine production systems to generate a dengue subunit vaccine candidate in tobacco. Chloroplast genome engineering was applied to express serotype-specific recombinant EDIII proteins in tobacco chloroplasts using both constitutive and ethanol-inducible expression systems. Expression of a tetravalent antigen fusion construct combining EDIII polypeptides from all four serotypes was also attempted. Transplastomic EDIII-expressing tobacco lines were obtained and homoplasmy was verified by Southern blot analysis. Northern blot analyses showed expression of EDIII antigen-encoding genes. EDIII protein accumulation levels varied for the different recombinant EDIII proteins and the different expression systems, and reached between 0.8 and 1.6 % of total cellular protein. Our study demonstrates the suitability of the chloroplast compartment as a production site for an EDIII-based vaccine candidate against dengue fever and presents a Gateway® plastid transformation vector for inducible transgene expression.
      PubDate: 2016-04-26
       
 
 
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