ANNOUNCEMENTS
Polyploidy has played a pivotal role in shaping plant genomes and enhancing phenotypic diversity through gene duplication and regulatory divergence. Among polyploid crops, Brassica species serve as an excellent model to study cis-regulatory evolution due to their complex sub-genomic architecture arising from whole genome triplication. The floral integrator gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) exists as three homeologous copies in Brassica, each derived from a distinct sub-genome—Least Fractionated (LF), Moderately Fractionated (MF1), and Most Fractionated (MF2). Despite conserved coding sequences, differential expression of these homeologs is driven by divergence in their promoter regions. The present study investigates the functional competence of the MF2-derived BjuSOC1 promoter in regulating flowering through a complementation assay in the Arabidopsis thaliana soc1-2 mutant background.
Transgenic lines expressing an MF2::AtSOC1 construct were developed, genotyped, and analyzed for transcript abundance using quantitative reverse transcription PCR (qRT-PCR). Phenotypic traits, including days to bolting and leaf number, were assessed to determine the extent of functional rescue. Results demonstrated that the MF2-derived promoter was capable of restoring SOC1 expression and normal flowering development in A. thaliana, though with variable efficiency across transgenic lines. These findings validate the MF2 promoter’s functional activity and support the hypothesis that cis-regulatory divergence following polyploidization contributes to expression diversity and phenotypic outcomes.
By providing direct evidence for the functional capability of a sub-genome-specific promoter, this study advances our understanding of regulatory evolution in polyploids and highlights the potential of promoter engineering for crop improvement.
Keywords: Polyploidy, Brassica, SOC1, cis-regulatory evolution, promoter complementation, MF2 sub-genome.
