Structural variation in the promoter region of DcSOC1d influences flowering behavior in carrot

Early flowering can lead to premature lignification of carrot roots, resulting in significant loss of commercial value. However, the molecular mechanisms controlling this trait remain poorly understood. In this study, we identified two SOC1 genes, DcSOC1b and DcSOC1d, located near the Vrn1 locus-a quantitative trait locus associated with early flowering habit in carrot. Both genes showed expression patterns consistent with early flowering in wild carrot 'Songzi' (SZ). Variations in the promoter region of DcSOC1d were identified between SZ and other biennial carrots. When DcSOC1d from SZ carrots, driven by its native promoter, was introduced into biennial 'Qitouhuang' (QTH) carrots, it exhibited high expression and induced flowering without vernalization. In contrast, DcSOC1b from SZ carrots showed low expression under the same conditions and failed to induce early flowering in QTH carrots. Further investigation found that DcSOC1d can upregulate DcSOC1b expression. Our findings provide novel insights into early flowering mechanisms that could be applied to carrot improvement through gene editing, with potential implications for other vegetable and fruit crops.