Abstract
Arabidopsis thaliana has 14 abscisic acid (ABA) receptors—PYR1/PYLs/RCARs—which have diverse and redundant functions in ABA signaling; however, the precise role of these ABA receptors remains to be elucidated. Here, we report the functional characterization of RCAR5/PYL11 in response to cold stress. Expression of RCAR5 gene in dry seeds and leaves was ABA-dependent and ABA-independent, respectively. Under cold stress conditions, seed germination was negatively affected by the level of RCAR5 expression, which was dependent on ABA and was regulated by HAB1, OST1, and ABI5—downstream components of RCAR5 in ABA signaling. Leaves of RCAR5-overexpressing plants showed enhanced stomatal closure—independent of ABA—and high expression levels of cold, dehydration, and/or ABA-responsive genes compared to those of wild-type; these traits conferred enhanced freezing tolerance. Our data suggest that RCAR5 functions in response to cold stress by delaying seed germination and inducing rapid stomatal closure via ABA-dependent and ABA-independent pathways, respectively.
Highlights
The plant hormone abscisic acid (ABA) plays a key role in growth and development, as well as in adaptive mechanisms to unfavorable conditions such as regulation of seed dormancy, germination, and stomatal opening and closure (Cutler et al, 2010; Hubbard et al, 2010)
We investigated expression levels of RCARs in dry seeds of Arabidopsis thaliana Columbia-0 (Col-0) and Landsberg erecta (Ler) ecotypes by quantitative reverse transcription-polymerase chain reaction analysis (Supplementary Figure S1A)
We focused on high-abundant RCAR genes in this study, of which RCAR1, RCAR2, RCAR5, and RCAR6 were significantly downregulated after imbibition (Supplementary Figures S1B, C)
Summary
The plant hormone abscisic acid (ABA) plays a key role in growth and development, as well as in adaptive mechanisms to unfavorable conditions such as regulation of seed dormancy, germination, and stomatal opening and closure (Cutler et al, 2010; Hubbard et al, 2010). ABA accumulates in seeds, inducing and maintaining seed dormancy and inhibiting seed germination by preventing water uptake and endosperm rupture (Müller et al, 2006; Seo et al, 2006). Drought stress induces ABA accumulation, leading to stomatal closure and induction of stress-related genes (Cutler et al, 2010). In Arabidopsis, ABA levels increase transiently and less markedly (2-fold) in response to cold stress than in response to drought stress (approximately 20-fold) (Lång et al, 1994). Several studies have shown that ABA is involved in cold stress responses; these studies have examined cold stress-induced ABA biosynthesis (Lång et al, 1994; Cuevas et al, 2008); absence of cold acclimation in ABA-deficient mutants (Gilmour and Thomashow, 1991; Xiong et al, 2001); and ABA induction of cold-responsive genes, mainly CBF genes (Knight et al, 2004; Lee and Seo, 2015)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
