GSE41433
Polypyrimidine tract-binding protein homologues from Arabidopsis are key regulators of alternative splicing with implications in fundamental developmental processes
Alternative splicing (AS) generates transcript variants by the definition of different exonic and intronic regions and causes a massive expansion of transcriptome diversity. Changes in AS patterns have been found to be linked to manifold biological processes, yet fundamental aspects such as the regulation of AS and the functional implications of altered AS programs largely remain to be addressed. In this work, widespread AS regulation by Arabidopsis Polypyrimidine tract-binding protein homologues (AtPTBs) was revealed. In total 452 AS events derived from 308 distinct genes were found to be responsive to the levels of the splicing factors AtPTB1 and AtPTB2, which predominantly triggered splicing of regulated introns, inclusion of cassette exons, and usage of upstream 5'' splice sites. In contrast, alternative 3'' splice site events were strongly underrepresented among the AtPTB1/2 targets and no major AS regulatory function of the distantly related AtPTB3 was found. Dependent on their position within the mRNA, AtPTB-regulated events can both modify the untranslated regions and give rise to alternative protein products. Gene ontology analysis revealed a connection of AtPTB-mediated AS control with diverse biological processes, and the functional implications of selected AS events were further elucidated in the context of seed germination and flowering time control. Specifically, AtPTB misexpression changes AS of the PHYTOCHROME INTERACTING FACTOR 6 (PIF6) pre-mRNA, coinciding with altered rates of abscisic acid-dependent seed germination. Furthermore, AS patterns as well as the expression of key flowering regulators were massively changed in an AtPTB1/2 level-dependent manner. In conclusion, our work has revealed widespread AS regulatory functions of the AtPTB splicing factors with important functional implications in various fundamental processes of Arabidopsis development. Overall design: Analysis of alternative splicing patterns in plants with increased and decreased levels of the 3 Arabidopsis Polypyrimidine-tract binding protein homologues in comparison to wild type samples, determined in duplicates