AtPPRT3, a novel E3 ubiquitin ligase, plays a positive role in ABA signaling

Key message The RING-type E3 ligase AtPPRT3 participates in the plant ABA responding as a positive regulator. E3 ubiquitin ligase, alike of classic plant stress resistance proteins, plays a vital role in regulating the degradation of stress-related proteins. In this study, we investigated the function of the RING-type E3 ubiquitin ligase AtPPRT3 in the ABA signaling pathway. AtPPRT3, located in the endoplasmic reticulum membrane, is involved in ABA signaling. The transcriptional expression ofAtPPRT3was induced by ABA, and the promoter region upstream ofAtPPRT3contains the ABA-responsive element (ABRE). Additionally, the beta-glucuronidase (GUS) gene driven by theAtPPRT3promoter was up-regulated in transgenic plants after ABA treated. We obtainedAtPPRT3function-deficient mutantsatpprt3-1,atpprt3-2, andAtPPRT3over-expressing lines (OE4 and OE5). In this study,atpprt3-1andatpprt3-2were less sensitive to exogenous ABA compared to Col-0, whereas OE4 and OE5 were more sensitive. Moreover, AtPPRT3 promotes ABA-mediated stomatal closure and inhibits water loss inArabidopsis thaliana. After exogenous ABA treated, the transcriptional expression levels ofAtDREB2A,AtKIN1,AtRD29A,AtERD10andAtRD29Bwere up-regulated to greater extents in OEs and lower extents inatpprt3-1andatpprt3-2compared to Col-0. These results suggest that AtPPRT3 positively regulates ABA signaling inA. thaliana.