Abstract

Brassica napus reproductive development and abiotic stress tolerance are critical for yield and quality, and characterizing key transcription factor families is vital for molecular breeding. Here, based on the B. napus cv. Darmor-bzh V5 reference genome, we systematically identified and analyzed the BnaS1fa gene family, uncovering 12 members. Their encoded proteins are mostly small, alkaline, stable, and hydrophilic, with a few having ultra-long structures. Phylogenetic analysis clustered them into three subfamilies; conserved motif and gene structure analyses revealed high overall family conservation with partial member differentiation. Promoter cis-acting element analysis showed enrichment in light, hormone, and stress-responsive elements. Chromosomal localization and intraspecific collinearity analyses indicated the family mainly derived from homologous fragment retention in A and C subgenomes. Transcriptome data demonstrated high BnaS1fa expression in late seed and silique development, with prominent heat stress responses. RT-qPCR, subcellular localization and transcriptional activity assays confirmed BnaS1fa9 and BnaS1fa10 as nuclear-localized transcription factors with heat stress-induced expression. This study elucidates BnaS1fa molecular characteristics and its potential roles in reproductive development and heat stress response, providing candidate genes for B. napus stress-resistant molecular breeding. Further functional validation of these key genes will facilitate the dissection of their precise regulatory mechanisms governing heat stress tolerance and reproductive growth, which can be ultimately applied to advance the genetic improvement of rapeseed stress resistance and yield performance.

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