Genome-wide identification and functional characterization of YTH domain-containing protein family genes in soybean

The YTH domain-containing protein family constitutes the primary class of readers for N6-methyladenosine modifications. Previous studies have highlighted their essential roles in plant responses to both biotic and abiotic stressors. However, the functions of YTH genes in soybean (Glycine max [L.] Merr.) remain largely unknown. Here, a genome-wide identification and comprehensive analysis of the GmYTH gene family in soybean is presented. Eighteen GmYTH genes were identified in the soybean genome, unevenly distributed across 11 chromosomes. Phylogenetic analysis grouped these genes into four distinct subfamilies. Notably, analysis of the promoter regions revealed that many GmYTH genes contained hormone- and stress-responsive regulatory elements. Functional analysis showed that GmYTH6 mutations in soybean improved root growth and salt tolerance. This was accompanied by higher antioxidant enzyme activities and lower levels of proline, hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) under salt stress. In contrast, reduced activities of the antioxidant enzymes and proline, together with elevated H₂O₂ and MDA levels, were observed in hairy roots overexpressing GmYTH6, correlating with their suppressed growth and diminished salt tolerance. RNA-seq analysis showed that GmYTH6 acts as an m⁶A-binding protein that likely influences salt-stress responses through transcriptional or post-transcriptional regulation of key pathways, including ribosome biogenesis and phenylpropanoid biosynthesis, including ABP19A, PER22, PER42, CXE15, BGLU12, and BGLU40. These findings provide valuable insights into the biological roles of GmYTH genes in soybean growth and their regulatory functions in salinity stress responses.