Identification of Pepper CaSBP08 Gene in Defense Response Against Phytophthora capsici Infection

Abstract

Little information is available on the role of Squamosa promoter binding protein (SBP)-box genes in pepper plants. This family of genes is known to have transcription characteristics specific to plants and to regulate plant growth, development, stress responses, and signal transduction. To investigate their specific effects in pepper (<i>Capsicum annuum</i>), we screened pepper SBP-box family genes (<i>CaSBP</i> genes) for <i>Phytophthora capsici</i> (<i>P. capsici</i>) resistance genes using virus-induced gene silencing. <i>CaSBP08</i>, <i>CaSBP11</i>, <i>CaSBP12</i>, and <i>CaSBP13</i>, which are associated with plant defense responses against <i>P. capsici</i>, were obtained from among fifteen identified <i>CaSBP</i> genes. The function of <i>CaSBP08</i> was identified in pepper defense response against <i>P. capsici</i> infection in particular. CaSBP08 protein was localized to the nucleus. Silencing of <i>CaSBP08</i> enhanced resistance to <i>P. capsici</i> infection. Following <i>P. capsici</i> inoculation, the malondialdehyde content, peroxidase activity, and disease index percentage of the <i>CaSBP08</i>-silenced plants decreased compared to the control. Additionally, the expression levels of other defense-related genes, especially those of <i>CaBPR1</i> and <i>CaSAR8.2</i>, were more strongly induced in <i>CaSBP08</i>-silenced plants than in the control. However, <i>CaSBP08</i> overexpression in <i>Nicotiana benthamiana</i> enhanced susceptibility to <i>P. capsici</i> infection. This work provides a foundation for the further research on the role of <i>CaSBP</i> genes in plant defense responses against <i>P. capsici</i> infection.