Localization and Functional Analysis of CtLTP8, an Extracellular Vesicle Protein That Enhances Resistance to Botrytis...

Safflower (Carthamus tinctorius L.) is an economically important crop, yet its production is severely threatened by fungal diseases including Botrytis cinerea. The molecular mechanism underlying disease resistance in safflower remains largely unclear. Extracellular vesicles (EVs), as vital carriers for cross-kingdom communication and transport, play crucial roles in plant antifungal defense. Lipid transfer proteins (LTPs), members of the pathogenesis-related protein 14 family, have also been shown to be key players in plant disease resistance. The promising resistance-related candidate gene CtLTP8 was previously identified via genome-wide association study (GWAS). In this study, a genome-wide analysis of the LTP gene family in safflower was performed. EVs were isolated from the apoplastic washing fluid of B. cinerea-infected safflower leaves, and proteomic analysis was performed. Numerous proteins associated with disease resistance, including CtLTP8, were detected by proteomic profiling. CtLTP8 was found to be present in EVs through molecular biological experiments. Moreover, stable overexpression of CtLTP8 in safflower significantly increased resistance to B. cinerea. In summary, this study characterized the disease resistance-related proteome of safflower EVs, and verified the presence of CtLTP8 in EVs and its antifungal function, providing valuable gene resources and theoretical support for safflower disease-resistance breeding and research on EV-mediated plant immune mechanisms.