Pepper ubiquitin‐specific protease, CaUBP12, positively modulates dehydration resistance by enhancing CaSnRK2.6 stability

SUMMARY Abscisic acid (ABA) is a plant hormone that activates adaptive mechanisms to environmental stress conditions. Plant adaptive mechanisms are complex and highly modulated processes induced by stress‐responsive proteins; however, the precise mechanisms by which these processes function under adverse conditions remain unclear. Here, we isolated CaUBP12 (Capsicum annuum ubiquitin‐specific protease 12) from pepper (C. annuum) leaves. We show that CaUBP12 expression is significantly induced after exposure to abiotic stress treatments. We conducted loss‐of‐function and gain‐of‐function genetic studies to elucidate the biological functions of CaUBP12 in response to ABA and dehydration stress. CaUBP12‐silenced pepper plants and CaUBP12‐overexpressing Arabidopsis plants displayed dehydration‐sensitive and dehydration‐tolerant phenotypes, respectively; these phenotypes were characterized by regulation of transpirational water loss and stomatal aperture. Under dehydration stress conditions, CaUBP12‐silenced pepper plants and CaUBP12‐overexpressing Arabidopsis plants exhibited lower and higher expression levels of stress‐related genes, respectively, than the control plants. We isolated a CaUBP12 interaction protein, CaSnRK2.6, which is a homolog of Arabidopsis OST1; degradation of this protein was partially inhibited by CaUBP12. Similar to CaUBP12‐silenced pepper plants and CaUBP12‐overexpressing Arabidopsis plants, CaSnRK2.6‐silenced pepper plants and CaSnRK2.6‐overexpressing Arabidopsis displayed dehydration‐sensitive and dehydration‐tolerant phenotypes, respectively. Our findings suggest that CaUBP12 positively modulates the dehydration stress response by suppressing CaSnRK2.6 protein degradation. Significance Statement This study reports the functional characterization of CaUBP12 in response to dehydration stress. CaUBP12 positively modulates the dehydration stress response by suppressing CaSnRK2.6 protein degradation. This study provides insight into the involvement of UBPs in the dehydration stress response, including modulation of transpirational water loss, stomatal aperture, and stress‐related gene expression.