Bioinformatic Identification and Expression Profiling of Heptahelical Transmembrane Protein Genes in Soybean Under Phytohormone and Nematode Stress

Heptahelical transmembrane proteins (HHPs) have recently been recognized as crucial regulators of diverse biological processes in eukaryotes. In this study, 10 GmHHP genes were identified in soybean, and a comprehensive analysis was conducted to examine their phylogenetic relationships, cis-regulatory elements, expression patterns, and potential regulatory networks. Expression profiling revealed that most GmHHP genes were transcriptionally induced by abscisic acid (ABA) and methyl jasmonate (MeJA), with GmHHP1 and GmHHP7 exhibiting the strongest induction. During soybean cyst nematode (SCN) infection, several GmHHP genes were down-regulated, suggesting a potential role in plant–nematode interactions. Protein interaction network analysis indicated that GmHHPs could interact with mitochondrial pyruvate carriers, alkaline phytoceramidases, and histone deacetylases, which may link them to ABA-regulated biological processes such as stomatal movement, water homeostasis, and stress adaptation. Furthermore, interacting miRNA prediction demonstrated that conserved miRNAs, including miR172 and miR319, might co-regulate GmHHP genes and their associated protein partners. Collectively, these findings indicate that GmHHP genes function as membrane-associated regulators of ABA signaling and defense responses, particularly under biotic stress, such as nematode infection.