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AELs suppress ABA signaling and responses by phosphorylating and destabilizing ABA receptors PYR/PYLs

ABSTRACT: Unveiling the signal transduction of phytohormone abscisic acid (ABA) will be greatly helpful to improve plant responses to stressful environment. ABA signaling is perceived and mediated by multi-member receptor PYR/PYLs, while whose post-translational modification, especially phosphorylation, is largely unknown. Here we demonstrated that Arabidopsis EL1-like (AEL), a casein kinase that regulates various physiological processes, phosphorylates PYR/PYLs and stimulates whose ubiquitination and degradation, leading to the suppressed ABA responses. Arabidopsis ael triple mutants display hypersensitive responses to ABA treatment, which is consistent with the suppressed degradation of PYR/PYL proteins. PYR/PYLs are phosphorylated in vivo and mutation of the conserved AEL-phosphorylation sites results in the reduced phosphorylation, ubiquitination, and degradation of PYR/PYLs, and hence the enhanced ABA responses. Our studies demonstrate the crucial roles of AEL-mediated phosphorylation in regulating the stability and function of PYR/PYLs and provide informative clues for elucidating the functional mechanism of ABA through regulating PYR/PYL receptors.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Arabidopsis Thaliana (mouse-ear Cress)

TISSUE(S): Plant Cell, Whole Body

SUBMITTER: li qu

LAB HEAD: Hongwei Xue

PROVIDER: PXD008565 | Pride | 2022-02-23

REPOSITORIES: Pride

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Project description:Abscisic acid (ABA) is a key hormone for plant growth, development and stress adaptation. Perception of ABA through four types of receptors has been reported. We show here that impairment of ABA perception through the PYR/PYL/RCAR branch reduces vegetative growth and seed production, and leads to a severely open stomata and dramatic ABA insensitive phenotype, even though other branches for ABA perception remain functional. Arabidopsis sextuple mutant impaired in 6 PYR/PYL receptors, namely PYR1, PYL1, PYL2, PYL4, PYL5 and PYL8, was able to germinate and grow even on 100 mM ABA. Whole-rosette stomatal conductance (Gst) measurements revealed that leaf transpiration in the sextuple pyr/pyl mutant was higher than in the ABA-deficient aba3-1 or ABA-insensitive snrk2.6 mutants. The gradually increasing Gst values of plants lacking three, four, five and six PYR/PYLs indicate quantitative regulation of stomatal aperture by this family of receptors. The sextuple mutant lacked ABA-mediated activation of SnRK2s and ABA-responsive gene expression was dramatically impaired as was reported in snrk2.2/2.3/2.6. In summary, these results show that ABA perception by PYR/PYLs plays a major role to regulate seed germination and establishment, basal ABA signaling required for vegetative and reproductive growth, stomatal aperture and transcriptional response to the hormone. Four biological replicates were generated for the 3 genotypes, pyr1pyl1pyl2pyl4pyl5pyl8 sextuple mutant, snrk2.2/2.3/2.6 triple mutant, and Col-0. All the samples were treated with ABA for 3 hours before harvesting. The four Col-0 samples were mix to create an unique reference Col-0 sample. Two comparasion were made, fisrt one, PYR/PYL sextuple mutant versus Col-0 reference sample and second one, SnRK2 triple mutant versus Col-0 reference sample. In each comparasion four biological replicates were made. Replicas number 1 and 2 were labeled with Cy5 for the mutant sample and Cy3 for the Col-0 reference sample, while the other two replicas,#3 and #4, were reversed-labeled.

Project description:ABA signaling relies on the perception of the hormone by 14 different members of the PYR/PYL/RCAR family of ABA receptors. Upon ABA binding, receptors become active in inhibiting a family of type 2C protein phosphatases that usually function as negative regulators on protein kinases of the SnRK2 family. Previous physiological and genetic data supporting a negative role exerted by nitric oxide (NO) on ABA signaling have been reported. Our preliminary data suggested that negative regulation exerted by NO on ABA signaling may involve direct effects of NO on ABA receptors. Here we explore whether the effects of NO on ABA signaling are due to post-translational modifications (PTMs) on ABA receptors. Two main PTMs are functionally related to NO, the S-nitrosylation of C residues and the nitration of Y residues and they have been studied in this work. Because our data suggest that NO can also modulate the stability of the receptor proteins, we have also analyzed another PTM, the ubiquitination of K residues. A double approach based on in vitro nitration of recombinant PYR/PYL/RCAR proteins as well as in planta expression of HA-tagged versions of the receptors, followed by immunopurification strategies based on anti-3-nitroY-coated magnetic beads, and LC-MS/MS analyses of the immunopurified proteins under non-reducing conditions allowed us to identify peptides containing nitroY (mass shifts of +45), S-nitrosylated C (mass shifts of +29), and K-GG tags resulting from the trypsin digestion of ubiquitin tails (mass shift of + 114). Our data suggest that S-nitrosylation of cysteines from PYR/PYL receptors occur in planta but has not effect on receptor function as tested in vitro. By contrast, the nitration of several Y residues of PYR/PYL receptors completely inactivates them, promotes also their polyubiquitination and marks them for subsequent proteasomal degradation, thus representing a rapid mechanism for lowering ABA sensitivity when required in the plant.

			Action	DRS
	col-PYL1-1.raw	Raw
	col-PYL1-ABA.msf	Msf
	col-PYL1-ABA.mzXML	Mzxml
	col-PYL1-ABA.pdResult	Other
	col-PYL1-ABA.raw	Raw

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AELs suppress ABA signaling and responses by phosphorylating and destabilizing ABA receptors PYR/PYLs

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