Cowpea Lipid Transfer Protein LTP1 Mediates Plant Resistance to Botrytis cinerea.

Plant lipid transfer proteins (LTPs), belonging to pathogenesis-related protein 14 family, participate in plant immune response to biotic stress. LTP1 from Vigna unguiculata was previously shown to be able to suppress infection by cowpea mosaic virus and soybean mosaic virus. However, whether cowpea LTP1 participates in the plant resistance to other plant pathogens remains unclear. The present study analyzed the role of LTP1 in plant resistance to eukaryotic pathogens. We observed that LTP1 overexpression in cowpea and tobacco significantly reduced lesion areas and biomass of the fungus Botrytis cinerea and oomycete Phytophthora capsici. Protein lipid overlay assay showed that LTP1 bound phosphatidic acid (PA) and phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P₂), but LTP1^3A, with three amino acids in the lipid binding domain being mutated to alanine, lost the lipid binding ability. Consistently, overexpression of LTP1^3A did not influence lesion areas and pathogen biomass in cowpea and tobacco plants after inoculation with B. cinerea at 48 hpi. LTP1 heterologous expression in tobacco induced significant increase in intracellular calcium, inositol 1,4,5-trisphosphate (IP₃) levels and abscisic acid (ABA) contents, leading to a more significant stomatal closure after B. cinerea infection. Overall, our findings suggest that cowpea LTP1 participates in the plant defense response through interacting with specific phospholipids, thereby interfering with pathological processes such as IP₃-mediated calcium signaling and stomatal movement.