Abstract
RNA splicing is a fundamental mechanism contributing to the definition of the cellular protein population in any given environmental condition. DNA-DAMAGE REPAIR/TOLERATION PROTEIN111 (DRT111)/SPLICING FACTOR FOR PHYTOCHROME SIGNALING is a splicing factor previously shown to interact with phytochrome B and characterized for its role in splicing of pre-mRNAs involved in photomorphogenesis. Here, we show that DRT111 interacts with Arabidopsis (Arabidopsis thaliana) Splicing Factor1, 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-ABI5. DRT111 is highly expressed in seeds and stomata of Arabidopsis and is induced by long-term treatments of polyethylene glycol and abscisic acid (ABA). DRT111 knock-out mutants are defective in ABA-induced stomatal closure and are hypersensitive to ABA during seed germination. Conversely, DRT111 overexpressing plants show ABA-hyposensitive seed germination. RNA-sequencing experiments show that in dry seeds, DRT111 controls expression and splicing of genes involved in osmotic-stress and ABA responses, 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 upregulated in imbibed seeds of drt111-2 mutants. Together, these results indicate that DRT111 controls sensitivity to ABA during seed development, germination, and stomatal movements, and integrates ABA- and light-regulated pathways to control seed germination.
Highlights
The phytohormone abscisic acid (ABA) regulates physiological and developmental processes, including stress responses, seed development, and germination
Using RNA transcriptome data from potato (Solanum tuberosum) cells adapted to gradually increasing concentrations of polyethylene glycol (PEG) we identified Arabidopsis orthologous genes, and functionally analysed their role in responses to ABA and osmotic stress (Ambrosone et al, 2015, 2017; Punzo et al, 2018)
When assessing responsiveness of DRT111 in seedlings exposed to short- or long-term treatments of NaCl, ABA, or PEG, we detected a significant up-regulation of DRT111 only after long-term treatments, whereas 3, 6, or 9-h treatments did not result in major changes of DRT111 transcript abundance
Summary
The phytohormone abscisic acid (ABA) regulates physiological and developmental processes, including stress responses, seed development, and germination. Perhaps the most well-defined mechanism mediated by ABA is induction of stomatal closure. In plants subjected to hyperosmotic stress, ABA is synthesized predominantly in leaf vascular tissues and guard cells. ABA activates a signalling pathway that coordinately modulates activity of membrane-located transporters, leading to efflux of solutes. The consequent reduction of guard cell turgor causes stomatal closure, reducing evapotranspiration under abiotic stress conditions (Bauer et al.,2013; Kuromori et al.., 2018; Nambara and Marion-Poll, 2005; Qin and Zeevaart, 1999; Schroeder et al, 2001). ABA induces maturation, dormancy, and plays a key role during germination
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