A B-Box Transcription Factor CoBBX24 from <i>Camellia oleifera</i> Delays Leaf Senescence and Enhances Drought Tolerance in <i>Arabidopsis</i>

Abstract

Plants face various biotic and abiotic stress factors during their growth and development, among which, drought is a serious adverse factor that affects yield and quality in agriculture and forestry. Several transcription factors are involved in regulating plant responses to drought stress. In this study, the B-box (BBX) transcription factor CoBBX24 was cloned from Camellia oleifera. This gene encodes a 241-amino-acid polypeptide containing two B-box domains at the N-terminus. A phylogenetic analysis revealed that CoBBX24 and CsBBX24 from Camellia sinensis are in the same branch, with their amino acid sequences being identical by 96.96%. CoBBX24 was localized to the nucleus and acted as a transcriptional activator. The overexpression of CoBBX24 in Arabidopsis heightened its drought tolerance along with a relatively high survival rate, and the rate of water loss in the OX-CoBBX24 lines was observably lower than that of the wild-type. Compared to the wild-type, the root lengths of the OX-CoBBX24 lines were significantly inhibited with abscisic acid. Leaf senescence was delayed in the OX-CoBBX24 lines treated with abscisic acid. The expression of genes related to leaf senescence and chlorophyll breakdown (e.g., SAG12, SAG29, NYC1, NYE1, and NYE2) was downregulated in the OX-CoBBX24 lines. This study indicated that CoBBX24 positively regulates the drought tolerance in Arabidopsis through delayed leaf senescence.

Keywords

• <i>Camellia oleifera</i>
• <i>CoBBX24</i>
• drought
• abscisic acid
• chlorophyll degradation