Project description:Autophagy is a conserved process in eukaryotes that contributes to cell survival in response to stress. Previously, we found that ER stress induces autophagy in a manner dependent upon IRE1b, an ER membrane-associated factor involved in the splicing of bZIP60 mRNA. IRE1 is a dual protein kinase and ribonuclease, and here we studied the involvement of the protein kinase catalytic domain, nucleotide binding and RNase domains of IRE1b in activating autophagy. Autophagy was assessed by quantifying the numbers of autophagosomes in transgenic Arabidopsis seedlings bearing mutations in the various IRE1b domains. The results showed that nucleotide binding and RNase activity of IRE1b are required for ER stress-mediated autophagy. The RNase activity is involved in IRE1b’s mRNA splicing function, but its principal splicing target, bZIP60, is not involved in IRE1b’s activation of autophagy. We therefore considered other roles for IRE1b in the activation of autophagy. Clustering of ER localized IRE1b-YFP was observed when seedlings were subjected to ER stress, and so we investigated whether IRE1b clustering induced autophagy. However, the RNase knockout mutation in IRE1b still undergoes clustering, suggesting that IRE1b clustering does not induce autophagy. In response to ER stress, the RNase of IRE1 has been found to engage in another activity called Regulated Ire1-Dependent Decay of Messenger RNA (RIDD), which is the promiscuous degradation of other mRNA in response to ER stress. By analyzing the RNA-seq data, 12 RIDD target genes were picked up for testing their role in inhibiting autophagy, and glucosidase 21 and peroxidase 14 are proved to be degraded to support the induction of autophagy by ER stress.
Project description:The oxt6 mutant is an oxidative stress-tolerant Arabidopsis mutant that is deficient in a polyadenylation factor subunit. Expression analysis suggests that impaired poly(A) site choice is responsible for the stress-tolerant phenotype. We used microarrays to understand the link between the polyadenylation defect and stress tolerance. Keywords: mutant, wild-type, complemented line comparison
Project description:Autophagy involves massive degradation of intracellular components and functions as a conserved system that helps cells to adapt to adverse conditions. In Arabidopsis thaliana, submergence induces the transcription of autophagy-related (ATG) genes and the formation of autophagosomes. To study the role of autophagy during submergence, we performed transcriptome analysis with atg5, an autophagy-defective mutant, under submergence conditions. Our data showed that submergence changed the expression profile of DEG in the atg5 versus wild-type.
Project description:We have implemented an integrated Systems Biology approach to analyze overall transcriptomic reprogramming and systems level defense responses in the model plant Arabidopsis thaliana during an insect (Brevicoryne brassicae) and a bacterial (Pseudomonas syringae pv. tomato strain DC3000) attack. The main aim of this study was to identify the attacker-specific and general defense response signatures in the model plant Arabidopsis thaliana while attacked by phloem feeding aphids or pathogenic bacteria. Defense responses and networks, unique and specific for aphid or Pseudomonas stresses were identified. Our analysis revealed a probable link between biotic stress and microRNAs in Arabidopsis and thus opened up a new direction to conduct large-scale targeted experiments to explore detailed regulatory links among them. The presented results provide a first comprehensive understanding of Arabidopsis - B. brassicae and Arabidopsis - P. syringae interactions at a systems biology level.