CaPHOT1 Negatively Regulates the Pepper Resistance to Phytophthora capsici Infection

Phototropins (PHOTs) are plant blue-light receptors that mediate crucial physiological processes such as phototropism, chloroplast movement, stomatal opening, and flowering. However, the PHOT family genes remain poorly characterized in pepper. Here, we identified and molecularly cloned two PHOT genes (CaPHOT1 and CaPHOT2) in pepper, which were phylogenetically classified into distinct groups with their homologs from rice, maize, tomato, and Arabidopsis. These genes exhibit conserved gene structures, implying functional conservation during evolution. Subcellular localization analysis confirmed that both CaPHOT1 and CaPHOT2 are localized to the plasma membrane. Expression profiling revealed that both CaPHOT1 and CaPHOT2 were expressed in all tissues, with the highest transcripts in leaves and the lowest in roots. Notably, RNA-seq data revealed that the expression of CaPHOT1 was up-regulated by JA and SA, whereas CaPHOT2 showed no significant changes. Furthermore, CaPHOT1 and CaPHOT2 displayed divergent expression patterns upon Phytophthora capsici infection (PCI). Furthermore, transient overexpression of CaPHOT1 in pepper enhanced susceptibility to PCI, indicating its negative role in disease resistance. Our findings identified the CaPHOT gene family in pepper and functionally demonstrated that CaPHOT1 negatively regulates resistance to PCI, thereby providing insights for future research on PHOTs in other plant species.