Controlled Activation of Auxilin-Like Protein 1 Triggers Cell Death-Associated Disease Resistance to <i>Xanthomonas oryzae</i> pv. <i>oryzae</i> in Rice

Auxilin-like proteins (ALPs) are Type III J-proteins that participate in clathrin-mediated endocytosis. In rice (Oryza sativa), an auxilin-like protein, OsALP1, has been identified, but its precise role in immunity and potential for application remain largely unknown. Here, we investigated OsALP1 and its close homolog OsALP2 to elucidate their roles in rice defense. OsALP1 and OsALP2 share high sequence similarity and similar overexpression phenotypes, including spontaneous cell death and enhanced resistance to Xanthomonas oryzae pv. oryzae (Xoo). Notably, OsALP1 transcript levels were higher than those of OsALP2 in the tissues and developmental stages examined in this study, suggesting that OsALP1 is the predominant functional ALP in rice. To separate OsALP1-mediated resistance from its detrimental growth effects, we established a dexamethasone (DEX)-inducible expression system enabling temporal activation of OsALP1 in planta. DEX-induced OsALP1 expression conferred enhanced resistance to Xoo but increased susceptibility to the necrotrophic fungus Rhizoctonia solani, revealing lifestyle-dependent outcomes of immune-associated cell death. These findings provide a controllable framework for deploying OsALP1-based disease resistance while minimizing growth costs.