Content area
Abstract
One of the biggest challenges for a plant’s survival is to deal with various abiotic and biotic stresses. During evolution many gene families related with stress responses have gone through expansion. However, the link between the expansion of these families and the adaptation of plants to environment is not clear. In my Ph.D. research I focused on the molecular evolution and function of two important gene families: 3RMYB and TIFY. 3R-MYB and TIFY genes were identified from ~70 plant species including algae and all major lineages of land plants. Duplication events giving rise to the expansion of the two families were identified and placed in the context of plant evolution and speciation. In the 3R-MYB project, I further explored the 3R-MYB motif and domain organization, gene structure, alternative splicing (AS), promoter, and their expression patterns under abiotic stresses. In the TIFY project, I focused on domain architecture evolution, rate-shift analysis in the domain which may contribute to functional divergence among subfamilies, and AS conservation and dynamics.
Jasmonic acid (JA) is a phytohormone induced by wound and herbivorous attack. Many MYB and TIFY genes play an important role in the jasmonate signaling pathway. In plants, AS, a posttranscriptional mechanism providing fast responses towards endogenous and exogenous stimuli, occurs within ~60% of the protein-coding genes in the genome. In my third project, I focused on jasmonate induced AS responses in Arabidopsis using transcriptome and proteome data. Three aspects of AS-related regulation were addressed: 1) differential expression of AS isoforms identified by a change in the proportion of AS isoforms from genes in response to methyl jasmonate (MeJA); 2) genes that undergo differential AS and produce isoforms with potential miRNA target sites; and 3) genes that undergo AS to produce splice variants with novel functions. I observed cases where AS alone or AS and transcription together can influence gene expression in response to jasmonate treatment. Twenty-one genes which show differential AS were also predicted to be differentially targeted by miRNAs. I identified 30 cases where alternative spliced isoforms may have novel functions. For example, AS of bHLH160 generates an isoform without a basic domain, which may convert it from an activator to a repressor.
