Genome-Wide Identification and Characterization of MYB Transcription Factors in Sudan Grass under Drought Stress

Sudan grass (<i>Sorghum sudanense</i> S.) is a warm-season annual grass with high yield, rich nutritional value, good regeneration, and tolerance to biotic and abiotic stresses. However, prolonged drought affects the yield and quality of Sudan grass. As one of the largest families of multifunctional transcription factors in plants, MYB is widely involved in regulating plant growth and development, hormonal signaling, and stress responses at the gene transcription level. However, the regulatory role of <i>MYB</i> genes has not been well characterized in Sudan grass under abiotic stress. In this study, 113 <i>MYB</i> genes were identified in the Sudan grass genome and categorized into three groups by phylogenetic analysis. The promoter regions of <i>SsMYB</i> genes contain different cis-regulatory elements, which are involved in developmental, hormonal, and stress responses, and may be closely related to their diverse regulatory functions. In addition, collinearity analysis showed that the expansion of the <i>SsMYB</i> gene family occurred mainly through segmental duplications. Under drought conditions, <i>SsMYB</i> genes showed diverse expression patterns, which varied at different time points. Interaction networks of 74 <i>SsMYB</i> genes were predicted based on motif binding sites, expression correlations, and protein interactions. Heterologous expression showed that <i>SsMYB8</i>, <i>SsMYB15</i>, and <i>SsMYB64</i> all significantly enhanced the drought tolerance of yeast cells. Meanwhile, the subcellular localization of all three genes is in the nucleus. Overall, this study provides new insights into the evolution and function of <i>MYB</i> genes and provides valuable candidate genes for breeding efforts in Sudan grass.