The pathogenicity and regulatory function of temperature-sensitive proteins PscTSP in Pseudofabraea citricarpa under high temperature stress

Abstract

Citrus fruit rich in beneficial health-promoting nutrients used for functional foods or dietary supplements production. However, its quality and yield were damaged by citrus target spot. Citrus target spot is a low-temperature fungal disease caused by Pseudofabraea citricarpa, resulting in citrus production reductions and economic losses. In this study, transcriptome and gene knockout mutant analyses were performed on the growth and pathogenicity of P. citricarpa under different temperature conditions to quantify the functions of temperature-sensitive proteins (PscTSP). The optimum growth temperature for P. citricarpa strain WZ1 was 20 °C, while it inhibited or stopped growth above 30 °C and stopped growth below 4 °C or above 30 °C. Certain PscTSP-key genes of P. citricarpa were identified under high temperature stress. qRT-PCR analysis confirmed the expression levels of PscTSPs under high temperature stress. PscTSPs were limited by temperature and deletion of the PscTSP-X gene leads to changes in the integrity of citrus cell walls, osmotic regulation, oxidative stress response, calcium regulation, chitin synthesis, and the pathogenicity of P. citricarpa. These results provide insight into the underlying mechanisms of temperature sensitivity and pathogenicity in P. citricarpa, providing a foundation for developing resistance strategies against citrus target spot disease.