Dynamic Transcriptomic Networks Underlying Early Bolting in Non-Heading Chinese Cabbage

Bolting time is a pivotal agronomic trait that determines the yield and commercial quality of Brassica rapa ssp. chinensis var. utilis. To investigate the molecular basis of early bolting, an early-bolting line 'm662' and a late-bolting line 't151' were used in this study. Phenotypic evaluation combined with shoot apical meristem (SAM) observation showed that 10 days of low-temperature vernalization markedly accelerated bolting in 't151'. Subsequently, SAM samples from 'm662', non-vernalized 't151', and 10-day vernalized 'V10-t151' were collected at five developmental stages (7, 10, 13, 16, and 19 d after transplanting) for transcriptome sequencing. Weighted gene co-expression network analysis revealed that key module genes related to gibberellin signaling were specifically enriched in 'm662' before bolting, whereas those in the middle and late bolting stages were enriched in hormone response, cell cycle regulation, and floral organ development. In 't151', hub genes detected at 7-13 d included three paralogs of the floral integrator gene SOC1 and BraA06.FPF1. BrSOC1 (BraA03g024230.4C) was significantly upregulated in response to vernalization. DEGs identified during the late developmental stage (16-19 d) included genes involved in transmembrane transport processes, flower development, reproductive shoot system development. Expression analysis across the three materials showed that vernalization accelerated bolting in 't151' by repressing BrFLC expression and promoting BrSOC1 expression. This study elucidates the dynamic transcriptomic network underlying early bolting in non-heading Chinese cabbage, providing key functional genes and mechanistic insights for bolting regulation and molecular breeding.