The Ectopic Expression of the Gene Enhances the Response of Plants from to Biotic Stress by Regulating the Defense Genes and Antioxidant Flavonoids

The Defective in Induced Resistance 1 () gene, a member of the lipid transferase proteins (LTPs), plays a crucial role in plant defense against pathogens. While previous transcriptomic studies have highlighted the significant expression of citrus LTPs during biotic stress, functional annotations of LTPs in the genera remain limited. In this study, we cloned the ( gene and overexpressed it in to evaluate its stress response mechanisms against biotic stress. The transgenic lines showed fewer disease symptoms in response to ( DC3000) compared to wild-type . Defense and pathogenesis-responsive genes such as , , , and were significantly induced, showing a 2- to 12-fold increase in all transgenic lines compared to the wild type. In addition, the DC3000-infected transgenic lines demonstrated elevated levels of flavonoids and salicylic acid (SA), along with higher expression of SA-related genes, compared to the wild type. Moreover, all transgenic lines possessed lower reactive oxygen species levels and higher activity of antioxidant defense enzymes such as superoxide dismutase, peroxidase, and catalase under DC3000 stress compared to the wild type. The up-regulation of defense genes, activation of the SA pathway, accumulation of flavonoids, and reinforcement of antioxidant defense mechanisms in transgenic lines in response to DC3000 underscore the critical role of in fortifying plant immunity. Thus, constitutes a promising candidate gene for improving bacterial disease resistance in commercial citrus cultivars.