Leucine-Rich Repeat Protein 13 Activates Immunity Against Ralstonia solanacearum and Thermotolerance in Pepper

Pepper (Capsicum annuum), a widely cultivated vegetable of significant economic importance globally, is frequently subjected to attacks from pathogens such as Ralstonia solanacearum, as well as high-temperature stress. However, the mechanisms by which pepper combats these stresses remain poorly understood. Herein, we reported that the expression of the leucine-rich repeat protein CaLRR13, which lacks a nucleotide-binding site (NBS), kinase domains, and a transmembrane region, was transcriptionally activated by both R. solanacearum inoculation and high-temperature stress. Through transient overexpression in the epidermal cells of Nicotiana benthamiana leaves, we found that CaLRR13 localized in both the cytoplasm and the nuclei. Reducing the expression of CaLRR13 via virus-induced gene silencing (VIGS) increased the sensitivity of pepper to R. solanacearum infection and high-temperature exposure, accompanied by reduced expression of immunity- and thermotolerance-related genes, including CaWRKY40, CaPR1, CaNPR1, CaDEF1, and CaHSP24. In contrast, transient overexpression of CaLRR13 in pepper leaves induced a like-hypersensitive response (HR) and enhanced the expression of the aforementioned immunity- and thermotolerance-related genes. Thus, we conclude that CaLRR13 plays a positive role in pepper immunity against R. solanacearum and thermotolerance, providing a new perspective on the crosstalk and management of plant responses to these two stresses.