Low temperature upregulates RoFLC through RoCBF to inhibit bolting and flowering in Rheum officinale Baill

To elucidate how low temperature affects yield in Rheum officinale Baill., yield measurements of perennial plants revealed that low temperature-induced bolting delay leads to increased production. However, the molecular mechanisms regulating flowering in medicinal rhubarb under low temperature conditions remain largely unexplored. Transcriptome analysis identified the key flowering-related gene RoFLC, which exhibits a conserved protein structure and is strongly induced under low temperature and late flowering conditions. Overexpression of RoFLC in Arabidopsis and tobacco further suppresses flowering delay and the expression of downstream florigen genes under low temperature.Further mechanistic studies revealed that RoFLC transcriptionally represses RoFT. Additionally, RoCBF1 directly binds to the promoter of RoFLC and activates its expression. Heterologous expression of RoCBF1 delayed flowering in Arabidopsis and tobacco under cold stress. Furthermore, overexpression of RoFLC rescued the early flowering phenotype of the Arabidopsis cbf1 mutant under low temperature, restoring a late flowering phenotype. Genetic evidence demonstrates that RoCBF1-dependent regulation of RoFLC is critical for mediating low temperature-induced flowering delay. These findings establish a linear regulatory pathway wherein low temperature-induced RoCBF1 activates RoFLC, which in turn represses RoFT, ultimately inhibiting flowering. This study offers crucial insights into the low-temperature flowering mechanism of R. officinale, with significant implications for both breeding strategies aimed at yield increase and agricultural practices supporting sustainability, thereby facilitating the growth of the rhubarb industry.