Functional analysis of StDIR27 and its upstream regulatory mechanism in potato resistance to Ralstonia solanacearum.

Plant Dirigent (DIR) proteins are increasingly recognized as key regulators in stress responses. Here, we identify StDIR27, a member of the DIR family in potato (Solanum tuberosum), as a critical positive regulator of resistance to Ralstonia solanacearum and various abiotic stresses. StDIR27 expression is strongly induced by bacterial wilt infection, drought, and high salinity, as well as by phytohormones including abscisic acid (ABA), methyl jasmonate (MeJA), gibberellic acid (GA), and salicylic acid (SA), with ABA showing the most potent induction. Overexpression of StDIR27 significantly enhances disease resistance, while silencing its homolog NbDIR27 in Nicotiana benthamiana leads to increased susceptibility. Biochemical and physiological analyses reveal that StDIR27 contributes to disease resistance by promoting lignin biosynthesis, strengthening cell wall integrity, and maintaining reactive oxygen species (ROS) homeostasis. Moreover, we demonstrate that the transcription factor StTCP14 directly binds to the StDIR27 promoter and activates its transcription. Together, our findings reveal a previously uncharacterized StTCP14-StDIR27 regulatory module that positively regulates plant immunity, offering novel insights into the molecular mechanisms of disease resistance and identifying potential targets for the genetic improvement of crop resilience.