Genome-Wide Analysis of FAR-RELATED SEQUENCES (FRS) Genes Related to Light Response in Soybean (Glycine max)

The FAR1-RELATED SEQUENCES (FRS) gene family plays a crucial role in light signaling, stress adaptation, and developmental regulation processes directly impacting crop growth and yield. This study identified 49 GmFRS genes unevenly distributed across 17 soybean chromosomes, phylogenetically classified into seven subgroups (I–VII), with subgroup VII forming an exclusive evolutionary subgroup alongside orthologs from Poaceae and Solanaceae. Members within each subfamily share conserved motif compositions and similar exon/intron structures. Gene duplication and selection pressure analyses revealed that the GmFRS family expanded primarily through WGD duplication events and then non-syntenic gene duplication, with all members evolving under purifying selection. Promoter analysis identified abundant cis-acting elements implicated in responses to light, phytohormones and other abiotic stimuli. Organ-/tissue-specific expression profiling demonstrated organ-preferential expression for family members, with the highest transcript levels observed in flowers (32.7%). Quantitative real-time PCR (qRT-PCR) analysis further indicated that the expression of most GmFRS genes is light-inducible and exhibits marked sensitivity to far-red light. This study may elucidate soybean FRS family functions in light signaling, development, and stress adaptation, while also providing foundational insights for molecular breeding in Glycine max.