MicroRNAs expression dynamics reveal post-transcriptional mechanisms regulating seed development in Phaseolus vulgaris L.

The knowledge on post-transcriptional regulation mechanisms implicated in seed development(SD)is still limited,particularly in one of the most consumed grain legumes,Phaseolus vulgaris L.We explore for the first time the miRNA expression dynamics in P.vulgaris developing seeds.Seventy-two known and 39 new miRNAs were found expressed in P.vulgaris developing seeds.Most of the miRNAs identified were more abundant at 10 and 40 days after anthesis,suggesting that late embryogenesis/early filling and desiccation were SD stages in which miRNA action is more pronounced.Degradome analysis and target prediction identified targets for 77 expressed miRNAs.While several known miRNAs were predicted to target HD-ZIP,ARF,SPL,and NF-Y transcription factors families,most of the predicted targets for new miRNAs encode for functional proteins.MiRNAs-targets expression profiles evidenced that these miRNAs could tune distinct seed developmental stages.MiRNAs more accumulated at early SD stages were implicated in regulating the end of embryogenesis,postponing the seed maturation program,storage compound synthesis and allocation.MiRNAs more accumulated at late SD stages could be implicated in seed quiescence,desiccation tolerance,and longevity with still uncovered roles in germination.The miRNAs herein described represent novel P.vulgaris resources with potential application in future biotechnological approaches to modulate the expression of genes implicated in legume seed traits with impact in horticultural production systems.

Shared and tailored common bean transcriptomic responses to combined fusarium wilt and water deficit

Common bean(Phaseolus vulgaris L.),one of the most consumed food legumes worldwide,is threatened by two main constraints that are found frequently together in nature,water deficit(WD)and fusarium wilt(Fop).To understand the shared and unique responses of common bean to Fop and WD,we analyzed the transcriptomic changes and phenotypic responses in two accessions,one resistant and one susceptible to both stresses,exposed to single and combined stresses.Physiological responses(photosynthetic performance and pigments quantification)and disease progression were also assessed.The combined FopWD imposition negatively affected the photosynthetic performance and increased the susceptible accession disease symptoms.The susceptible accession revealed a higher level of transcriptional changes than the resistant one,and WD single stress triggered the highest transcriptional changes.While 89 differentially expressed genes were identified exclusively in combined stresses for the susceptible accession,35 were identified in the resistant one.These genes belong mainly to“stress”,“signaling”,“cell wall”,“hormone metabolism”,and“secondary metabolism”functional categories.Among the up-regulated genes with higher expression in the resistant accession,the cysteine-rich secretory,antigen 5 and Pr-1(CAP)superfamily protein,a ribulose bisphosphate carboxylase family protein,and a chitinase A seem promising targets for multiple stress breeding.

XBAT35, a Novel Arabidopsis RING E3 Ligase Exhibiting Dual Targeting of Its Splice Isoforms, Is Involved in Ethylene-Mediated Regulation of Apical Hook Curvature

The Arabidopsis XBAT35 is one of five structurally related ankyrin repeat-containing Really Interesting New Gene （RING） E3 ligases involved in ubiquitin-mediated protein degradation, which plays key roles in a wide range of cel- lular processes. Here, we show that the XBAT35 gene undergoes alternative splicing, generating two transcripts that are constitutively expressed in all plant tissues. The two splice variants derive from an exon skipping event that excludes an in-frame segment from the XBAT35 precursor mRNA, giving rise to two protein isoforms that differ solely in the presence of a nuclear localization signal （NLS）. Transient expression assays indicate that the isoform lacking the NLS localizes in the cytoplasm of plant cells, whereas the other is targeted to the nucleus, accumulating in nuclear speckles. Both isoforms are functional E3 ligases, as assessed by in vitro ubiquitination assays. Two insertion mutant alleles and RNA-interference （RNAi） silencing lines for XBAT35 display no evident phenotypes under normal growth conditions, but exhibit hyper- sensitivity to the ethylene precursor 1-aminocyclopropane-l-carboxylate （ACC） during apical hook exaggeration in the dark, which is rescued by an inhibitor of ethylene perception. Independent expression of each XBAT35 splice variant in the mutant background indicates that the two isoforms may differentially contribute to apical hook formation but are both functional in this ethylene-mediated response. Thus, XBAT35 defines a novel player in ethylene signaling involved in negatively regulating apical hook curvature, with alternative splicing controlling dual targeting of this E3 ubiquitin ligase to the nuclear and cytoplasmic compartments.

Improving the haploidization toolbox:Maternal factors take the stage

Plant breeders have a great interest in obtaining plants that are genetically homogeneous as quickly as possible,with high efficiency and at low cost.Conventional approaches,including selfing or backcrossing,cannot provide this.Haploid technologies,however,offer a solution and are therefore the subject of intensive research,in particular during the last decade.