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 <i>PHOT</i> family genes remain poorly characterized in pepper. Here, we identified and molecularly cloned two <i>PHOT</i> genes (<i>CaPHOT1</i> and <i>CaPHOT2</i>) in pepper, which were phylogenetically classified into distinct groups with their homologs from rice, maize, tomato, and <i>Arabidopsis</i>. 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 <i>CaPHOT1</i> and <i>CaPHOT2</i> 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 <i>CaPHOT1</i> was up-regulated by JA and SA, whereas <i>CaPHOT2</i> showed no significant changes. Furthermore, <i>CaPHOT1</i> and <i>CaPHOT2</i> displayed divergent expression patterns upon <i>Phytophthora capsici</i> infection (PCI). Furthermore, transient overexpression of <i>CaPHOT1</i> in pepper enhanced susceptibility to PCI, indicating its negative role in disease resistance. Our findings identified the <i>CaPHOT</i> gene family in pepper and functionally demonstrated that <i>CaPHOT1</i> negatively regulates resistance to PCI, thereby providing insights for future research on <i>PHOTs</i> in other plant species.