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Alternative splicing in developmental control and stress response in Arabidopsis thaliana

Final Activity Report Summary - ASA (Alternative Splicing in Developmental Control and Stress Response in Arabidopsis thaliana)

Alternative splicing (AS) has recently emerged as one of the most important mechanisms for generating proteome diversity and regulating gene expression. Very few examples of alternatively-spliced transcripts have been reported in plants and still fewer are known to generate functionally distinct proteins. However, recent bioinformatics studies indicate that AS plays a far more important role in plants than previously thought and further work is necessary to uncover the significance and regulation of this process. This project aimed at investigating both the biological relevance of AS in plant development and stress responses and the regulatory mechanisms of plant pre-mRNA splicing about which virtually nothing is known.

Analysis of the tissue-specific expression patterns of all 19 Arabidopsis serine / arginine-rich (SR) proteins, which are established key players in mammalian AS, revealed that most display alternative transcripts and are highly expressed in flowers. In addition, the majority of these genes are induced by abiotic stress, pointing to a role for SR proteins in plant responses to the environment. Functional analysis of this protein family using reverse genetics is underway. A knockout mutant of a plant-specific SR protein displays pleiotropic phenotypic changes and altered sensitivity to sugars, indicating an essential role for this splicing factor in normal plant development and in the glucose signalling pathway. Moreover, we identified a novel E3 ubiquitin ligase that undergoes alternative splicing. Exon skipping of its pre-mRNA, determines subcellular localisation of two splice isoforms. Loss of function mutants for this gene display a subtle phenotype in the presence of ethylene, and the discovery of a highly homologous Arabidopsis gene has prompted the generation of a double mutant, which is currently being characterised.

Results from this work are accelerating the understanding of the molecular mechanisms underlying plant adaptation to the environment, opening new avenues for the use of biotechnology to increase plant productivity.