Genome-Wide Identification of the MYB Transcription Factor Family in Schima superba and Functional Analysis of SsMYB24 in Drought Stress Response

Schima superba, belonging to the genus Schima of Theaceae, is a common large tree in evergreen broad-leaved forests in subtropical regions of China. As one of the largest transcription factor families in plants, MYB transcription factors play an important role in plant stress response by specifically binding to cis-acting elements in different gene promoter regions to accurately regulate gene expression. However, there are few studies on MYB transcription factors in S. superba. The MYB transcription factor family of S. superba was found and examined in this study using the genomic and transcriptome data of the S. superba. A set of 220 MYB transcription factors was identified from S. superba and classified into four subfamilies. These transcription factors were unevenly distributed on 18 chromosomes of S. superba. The conserved domains of the same subfamily members are highly similar to the conserved motifs. The collinearity analysis between species showed that there were few orthologous genes located on chromosome 18 of S. superba. Numerous elements linked to phytohormone response, stress adaptation, and growth control can be found in the promoter regions of the S. superba MYB transcription factor family, according to an analysis of the promoter cis-acting elements. Verification via qRT-PCR showed that among 15 SsMYBs genes tested, SsMYB24 expression peaked at 96 h of drought stress, followed by a rapid downregulation upon rewatering to initial levels. This expression pattern aligned with the transcriptome data. This study is helpful to further identify the function of SsMYB transcription factors and provide a new molecular mechanism for improving drought tolerance of S. superba.