Genome-wide identification and gene expression analysis of Formin homology 2 (FH2) genes in peanut

The Formin homology 2 (FH2) family plays a crucial role in regulating actin cytoskeleton dynamics and plant responses to abiotic stress. However, the evolutionary mechanisms and functional characteristics of the FH2 family in cultivated peanut (Arachis hypogaea) remain largely unclear, particularly under heavy metal and salt stress. In this study, 29 AhFH2 genes were identified in the peanut genome. Phylogenetic analysis classified these genes into five major subfamilies. Synteny analysis showed that segmental duplication was the main driving force underlying expansion of the AhFH2 gene family in allotetraploid peanut, and that these genes have undergone strong purifying selection to preserve their core functions. Furthermore, quantitative analysis of AhFH2 homoeologous gene pairs revealed significant subgenome-specific expression bias, likely suggesting functional divergence and subfunctionalization during polyploid evolution. Cis-regulatory element analysis identified multiple motifs associated with hormone signaling and stress responses. In addition, qRT-PCR expression profiling and protein–protein interaction (PPI) network analysis showed that AhFH2 genes exhibited significant tissue specificity and transcriptional divergence under five abiotic stresses, including aluminum, cadmium, salt, selenium, and manganese. Notably, AhFH2-6 and AhFH2-25 were identified as core stress-responsive candidate genes that mediate responses to heavy metal toxicity in peanut roots. This study provides the first comprehensive overview of the evolutionary landscape of the FH2 family in cultivated peanut and highlights potential subgenome-biased expression under stress conditions. These findings provide insight into Formin-mediated molecular networks underlying crop stress tolerance and identify promising candidate targets for future genetic improvement of peanut through gene editing.