Identification and Characterization of the MAPK Genes in Sorghum and Their Expression in Response to Aphid Infestation

Mitogen-activated protein kinase (MAPK) cascades are key signaling components that regulate plant growth, development and responses to stresses. In this study, 19 sorghum MAPK genes (SbMAPKs) were identified through comprehensive bioinformatic analyses, including sequence alignment, gene structure characterization, conserved motif analysis and phylogenetic analysis. Phylogenetic analysis classified the SbMAPK family into five subfamilies (A–E). Evolutionary analyses suggested that tandem duplication, along with strong purifying selection, contributed to the expansion and conservation of the SbMAPK gene family in sorghum. Promoter analysis revealed that most SbMAPKs contain predicted cis-regulatory elements associated with phytohormone signaling and biotic and abiotic stress responses. Furthermore, quantitative real-time PCR (qRT-PCR) analysis identified nine SbMAPK genes that were differentially expressed following sorghum aphid infestation. Among these, SbMAPK4 consistently exhibited higher expression in the resistant genotype, suggesting a potential role in aphid-induced defense responses. These findings identify candidate SbMAPKs for functional characterization and provide new insights into the evolution of the MAPK gene family, laying the groundwork for elucidating the molecular mechanisms underlying aphid resistance and supporting the genetic improvement of sorghum.