Genome-Wide Analysis of the JAZ Gene Family in Potato and Functional Verification of StJAZ23 Under Drought Stress

The JASMONATE-ZIM DOMAIN (JAZ) repressors are crucial proteins in the jasmonic acid signaling pathway that play a significant role in plant growth, development and response to abiotic stress (such as drought, heat, salinity, and low temperature). In this study, we identified 26 potato JAZ genes and classified the corresponding predicted proteins into five subfamilies. All potato JAZ proteins exhibited the expected conserved TIFY (TIF[F/Y] XG) and JAZ domains. Additionally, we identified several stress-responsive cis-regulatory elements, notably ABRE and ARE in the promoters of the JAZ gene family. Whole transcriptome and gene family expression analysis identified StJAZ23 as a key gene responding to drought stress in the root tissues of the Atlantic (Atl) and Qingshu 9 (QS9) potato cultivars. The StJAZ23 gene was cloned, and subcellular localization analysis suggested that the StJAZ23 protein was mainly localized in the nucleus and cell membrane. This study confirmed that StJAZ23 plays a role in drought stress by analyzing several StJAZ23 overexpression (OE-3, OE-5, and OE-6) and RNA interference (RNAi-3, RNAi-6, and RNAi-13) transgenic potato lines. The OE lines displayed significantly increased StJAZ23 expression compared to wild-type (WT) plants, while RNAi lines exhibited significantly reduced expression. The total root length, root tip count, and root surface area were significantly enhanced in OE lines under drought stress, compared to WT plants, whereas RNAi lines showed significant reductions. StJAZ23 overexpression also increased the activities of SOD, POD, CAT, and root vigor under drought stress and JA and ABA hormone levels were also significantly increased in roots under drought stress. These results highlight the positive role of the StJAZ23 gene in enhancing potato resilience to drought stress.