Overexpression of Solanum tuberosum respiratory burst oxidase homolog A (StRbohA) promotes potato tolerance to Phytophthora infestans.

Reactive oxygen species (ROS) represent one of the first lines of plants' biochemical defense against pathogens. Plants' respiratory burst oxidase homologs (RBOHs) produce ROS as by-products in several cellular compartments. In potato tubers, Solanum tuberosum respiratory burst oxidase homolog (StRBOHs) are involved in suberization and healing of wounded tissues. StRbohA has been tested in the model plant Arabidopsis thaliana, which led to enhanced plant defense against the soil-borne pathogen Verticillium dahliae. Here, we showed that overexpressing StRbohA in potato plants enhancesd plant tolerance to the oomycete Phytophthora infestans, the causal agent of late blight disease. Transgenic potato plants expressing StRbohA showed reduced disease symptoms (necrosis) compared to the wild type check. The In parallel, the expression of pathogenesis-related genes (PRs), RBOHs, antioxidation-related genes CPRX1, PRX2, APRX1, CAT1, and CAT2, and genes involved in the biosynthesis pathways of jasmonic and salicylic acids (ICS, PAL1, PAL2, LOX1, LOX2, and LOX3) exhibited significant increases in the transgenic plants in response to infection. Following higher expression of RBOHs, ROS accumulated more in inoculation sites of the transgenic plants. ROS act as signals that activate gene expression in the SA biosynthesis pathway, leading to the accumulation of SA and triggering SA-based defense mechanisms. SA-responsive pathogenesis-related genes (PRs) showed higher expression in the transgenic plants, which resulted in the restriction of pathogen growth in plant tissues. These results represent a demonstration of the effective role of StRbohA in enhancing potato defense against P. infestans.