OfWRKY17-OfC3H49 module responding to high ambient temperature delays flowering via inhibiting OfSOC1B expression in Osmanthus fragrans

Ambient temperature is a pivotal factor in the regulation of the flowering process in plants. In this study, we found that high ambient temperature exerts an inhibitory effect on the flowering of Osmanthus fragrans "Sjigui". However, the underlying molecular mechanisms remain not fully understood. Through transcriptome analysis, a differently expressed C3H gene OfC3H49 was identified, which is induced by high ambient temperature. OfC3H49 was demonstrated to delay the flowering process of Arabidopsis and downregulate the expression of flowering-related genes in O. fragrans calli. Further investigation indicates that OfC3H49 as a transcriptional repressor directly suppresses the expression of the OfSOC1B thereby causing a delay in flowering time. Furthermore, a WRKY transcription factor, OfWRKY17, was identified to be responsive to high ambient temperature, directly binding to the OfC3H49 promoter and enhance OfC3H49 expression. Overexpression of OfWRKY17 in Arabidopsis resulted in a significant delay in flowering and induced the expression of OfC3H49 in O. fragrans calli. Collectively, our findings delineate a regulatory module, OfWRKY17-OfC3H49, which is activated by high ambient temperature and functions as a negative regulator of flowering by suppressing the expression of OfSOC1B in O. fragrans. This study provides novel insights into the molecular mechanisms involved in ambient temperature-mediated flowering control and contributes to the development of molecular breeding strategies for O. fragrans.