DRT111/SFPS splicing factor controls ABA sensitivity in Arabidopsis seed development and germination

Abstract

RNA splicing is a fundamental mechanism contributing to the definition of the cellular protein population in any given environmental condition. DRT111/SFPS is a splicing factor previously shown to interact with phytochromeB and characterized for its role in splicing of pre-mRNAs involved in photomorphogenesis. Here, we show that DRT111 interacts with Arabidopsis Splicing Factor 1 (SF1), involved in 3 splicing site recognition. Double and triple mutant analysis shows that DRT111 controls splicing of ABI3 and acts upstream of the splicing factor SUPPRESSOR OF ABI3-5 (SUA). DRT111 is highly expressed in seeds and stomata of Arabidopsis and is induced by long-term treatments with polyethylene glycol and ABA. DRT111 knock-out mutants are defective in ABA-induced stomatal closure and are hypersensitive to ABA during seed germination. Conversely, DRT111 over-expressing plants show ABA hyposensitive seed germination. RNAseq experiments show that in dry seeds, DRT111 controls expression and splicing of genes involved in response to osmotic stress and ABA, light signaling and mRNA splicing, including targets of ABSCISIC ACID INSENSITIVE3 (ABI3) and PHYTOCHROME INTERACTING FACTORs (PIFs). Consistently, expression of the germination inhibitor SOMNUS, induced by ABI3 and PIF1 is up-regulated in imbibed seeds of drt111-2 mutants. Altogether, these results indicate that DRT111 controls sensitivity to abscisic acid (ABA) during seed development, germination and stomatal movements and constitutes a point of integration of the ABA- and light-regulated pathways to control seed germination. One Sentence SummaryArabidopsis splicing factor DRT111/SFPS is required for ABA-mediated responses in seeds