Study of Function and Regulatory Factors of CaPEX3 in the Regulation of Pollen Viability in Pepper (Capsicum annuum L.)

The vitality of pollen significantly influences the efficiency of pollination and microspore embryogenesis. Mining genes associated with pollen vitality will help accelerate pepper (<i>Capsicum annuum</i> L.) breeding progress via genetic engineering. <i>PEX</i> (<i>pollen extensin-like</i>), a member of the LRX (leucine-rich repeat extensin) family, is predominantly expressed in pollen and participates in regulating pollen vitality. However, its function and regulatory factors in pepper remain elusive. In this study, GUS histochemical staining results revealed that pepper <i>CaPEX3</i> could be expressed in petals, sepals, anthers, and pollens of transgenic tomato (<i>Solanum lycopersicum</i> L.) lines expressing <i>CaPEX3 promoter</i>::<i>GUS</i>. Moreover, inhibition of the <i>CaPEX3</i> by virus-induced gene silencing (VIGS) in pepper resulted in reduced pollen germination rate and viability, while overexpression of <i>CaPEX3</i> in tomato significantly enhanced germination rate and pollen viability. In addition, <i>TRANSPARENT TESTA GLABRA 1</i> (<i>CaTTG1</i>) and <i>Nuclear transcription factor Y subunit C9</i> (<i>CaNFYC9</i>) were screened out and identified as the upstream regulatory transcription factors of <i>CaPEX3</i> through yeast one-hybrid (Y1H) screening and dual-luciferase reporter (Dual-LUC) assays. Taken together, the identification of transcription factors may reveal a more comprehensive mechanism underlying <i>CaPEX3</i>-mediated enhancement of pepper pollen viability. This study not only provides genetic resources for pollen viability research but also establishes a theoretical foundation for pepper breeding.