Serine/arginine-rich(SR)proteins are conserved splicing regulators that play important roles in plant stress responses,namely those mediated by the abscisic acid(ABA)hormone.The Arabidopsis thaliana SR-like protein SR...Serine/arginine-rich(SR)proteins are conserved splicing regulators that play important roles in plant stress responses,namely those mediated by the abscisic acid(ABA)hormone.The Arabidopsis thaliana SR-like protein SR45 is a described negative regulator of the ABA pathway during early seedling development.How the inhibition of growth by ABA signaling is counteracted to maintain plant development under stress conditions remains largely unknown.Here,we show that SR45 overexpression reduces Arabidopsis sensitivity to ABA during early seedling development.Biochemical and confocal microscopy analyses of transgenic plants expressing fluorescently tagged SR45 revealed that exposure to ABA dephosphorylates the protein at multiple amino acid residues and leads to its accumulation,due to SR45 stabilization via reduced ubiquitination and proteasomal degradation.Using phosphomutant and phosphomimetic transgenic Arabidopsis lines,we demonstrate the functional relevance of ABA-mediated dephosphorylation of a single SR45 residue,T264,in antagonizing SR45 ubiquitination and degradation to promote its function as a repressor of seedling ABA sensitivity.Our results reveal a mechanism that negatively autoregulates ABA signaling and allows early plant growth under stress via posttranslational control of the SR45 splicing factor.展开更多
基金This work was funded by the Fundac¸ao para a Ciencia e a Tecnologia(FCT)through grant PTDC/ASP-PLA/2550/2021 and a PhD fellowship PD/BD/128401/2017 awarded to R.A.-M.Funding from the research unit GREEN-it"Bioresources for Sustainability"(UIDB/04551/2020)is also acknowledgedA.M.J.and J.R.were funded by the Gatsby Charitable Foundation and BBSRC(BB/P018572/1).
文摘Serine/arginine-rich(SR)proteins are conserved splicing regulators that play important roles in plant stress responses,namely those mediated by the abscisic acid(ABA)hormone.The Arabidopsis thaliana SR-like protein SR45 is a described negative regulator of the ABA pathway during early seedling development.How the inhibition of growth by ABA signaling is counteracted to maintain plant development under stress conditions remains largely unknown.Here,we show that SR45 overexpression reduces Arabidopsis sensitivity to ABA during early seedling development.Biochemical and confocal microscopy analyses of transgenic plants expressing fluorescently tagged SR45 revealed that exposure to ABA dephosphorylates the protein at multiple amino acid residues and leads to its accumulation,due to SR45 stabilization via reduced ubiquitination and proteasomal degradation.Using phosphomutant and phosphomimetic transgenic Arabidopsis lines,we demonstrate the functional relevance of ABA-mediated dephosphorylation of a single SR45 residue,T264,in antagonizing SR45 ubiquitination and degradation to promote its function as a repressor of seedling ABA sensitivity.Our results reveal a mechanism that negatively autoregulates ABA signaling and allows early plant growth under stress via posttranslational control of the SR45 splicing factor.
