Genome-Wide Identification and Characterization of RopGEF Gene Family in C4 Crops

In plants, RopGEF-mediated ROP signaling is pivotal in cellular signaling pathways, including apical growth, pollen germination and perception, intercellular recognition, as well as in responses to biotic and abiotic stresses. In this study, we retrieved a total of 37 RopGEF members from three C₄ Crops, of which 11 are from millet, 11 from sorghum, and 15 from maize. Based on their phylogenetic relationships and structural characteristics, all RopGEF members are classified into four subfamilies. The qRT-PCR technique was utilized to evaluate the expression profiles of 11 <i>SiRopGEFs</i> across different tissues in foxtail millet. The findings indicated that the majority of the <i>SiRopGEFs</i> exhibited higher expression levels in leaves as opposed to roots and stems. The levels of expression of <i>SiRopGEF</i> genes were examined in response to abiotic stress and plant hormones. <i>SiRopGEF1</i>, <i>SiRopGEF5</i>, <i>SiRopGEF6</i>, and <i>SiRopGEF8</i> showed significant induction under abiotic stresses such as salt, cold, and heat. On the other hand, <i>SiRopGEF1</i>, <i>SiRopGEF2</i>, and <i>SiRopGEF7</i> were consistently upregulated, while <i>SiRopGEF3</i>, <i>SiRopGEF4</i>, <i>SiRopGEF6</i>, <i>SiRopGEF9</i>, and <i>SiRopGEF10</i> were downregulated upon exposure to abscisic acid (ABA), ethylene (ET), salicylic acid (SA), and gibberellic acid (GA₃) hormones. The alterations in the expression patterns of RopGEF members imply their potential functions in plant growth and development, abiotic stress response, and hormone signal transduction. These discoveries suggest that the <i>RopGEF</i> genes may function as a potential genetic marker to facilitate future studies in elucidating the functional characteristics of RopGEFs.