Project description:Plant microRNAs (miRNAs) have been implicated in plant immunity. These mainly focusing Arabidopsis thaliana threatened by (hemi-)biotrophic pathogens such as the bacterial pathogen Pseudomonas syringae. Here, we show that the Arabidopsis miRNA pathway is important for defense responses against the necrotrophic fungus Alternaria brassicicola. The miRNA pathway mutant ago1 exhibits an exaggerated response when treated with A. brassicicola, proposing that AGO1 is positive regulator. We found a subset of Arabidopsis miRNAs that quickly change their expression and their abundance in AGO1 complexes in plants exposed to A. brassicicola. The miRNAs responding to pathogen treatment are mainly targeting genes encoding metabolic enzymes, proteins involved protein degradation or transposons. In case of miR163, A. brassicicola infection results in increased levels of miRNA precursors and preferential accumulation of an unspliced form of pri-miR163, suggesting that A. brassicicola infection changes the transcriptional and post-regulation of pri-miRNAs. miR163 acts as a negative regulator of plant defense because mir163 mutants are more resistant when treated with A. brassicicola. Taken together, our results reveal the existence of positively and negatively acting Arabidopsis miRNA modulating the defense responses against A. brassicicola and highlight the importance of host miRNAs in the interaction between plants and necrotrophic pathogens.
Project description:Although abscisic acid (ABA) and gibberellins (GAs) play pivotal roles in many physiological processes in plants, their interaction in the control of leaf growth remains elusive. In this study, genetic analyses of ABA and GA interplay in leaf growth were performed in Arabidopsis thaliana. The results indicate that for ABA and GA interaction, leaf growth of both the aba2/ga20ox1 and aba2/GA20OX1-OE plants exhibits partially additive effects but is similar to the aba2 mutant. Consistent with this result, transcriptome analysis suggests that a substantial proportion (45-65%) of the gene expression profile of aba2/ga20ox1 and aba2/GA20OX1-OE plants overlaps and shares a similar pattern to the aba2 mutant. Thus, these data support that ABA deficiency dominates leaf growth regardless of GA levels. Moreover, gene ontology (GO) analysis indicates gene enrichment in the categories of hormone response, developmental and metabolic processes, and cell wall organization in these three genotypes. Leaf developmental genes are also involved in ABA-GA interaction. Collectively, these data support that the genetic relationship of ABA and GA interaction involves multiple coordinated pathways rather than a simple linear pathway in the regulation of leaf growth. To better understand the molecular basis of ABA and GA interaction, transcriptome analysis was performed among the genotypes used in this study.