The essential role of the hickory StMADS11 subfamily in flower organogenesis and flowering time in Arabidopsis

The StMADS11 subfamily genes play a crucial role in regulating flowering time, flower development, and bud dormancy in plants. These genes exhibit functional differences between annual and perennial woody plants. In hickory (Carya cathayensis Sarg.), the specific roles of these genes in flowering regulation have not been elucidated. In this study, we identified five StMADS11 subfamily genes in the hickory genome, designated as CcSVP-like, CcAGL24-like1, CcAGL24-like2, CcJOINTLESS-like1, and CcJOINTLESS-like2, based on their clustering characteristics. Sequence analyses revealed distinct structural features in this subfamily, including differences in intron length, C domain, and conserved motifs. Transcript analysis indicated high expression levels of these genes in female flower buds, along with a notable seasonal expression pattern. Overexpression studies on Arabidopsis have demonstrated that the StMADS11 subfamily genes lead to various floral organ and pod anomalies. Specifically, overexpression of CcSVP-like resulted in delayed flowering, while overexpression of CcAGL24-like1, CcAGL24-like2, CcJOINTLESS-like1, and CcJOINTLESS-like2 promoted flowering. Protein interaction studies have shown that the StMADS11 subfamily proteins bind to the CcFUL-like protein. Notably, CcFUL-like, CcSVP-like, CcJOINTLESS-like1, and CcJOINTLESS-like2 proteins were able to bind to the CcSOC1-like promoter and suppress its expression. Our findings elucidate the distinct roles of the StMADS11 subfamily genes in flower development and timing, contribute to developing the current understanding of flowering regulation in hickory, and offer a foundation for further studies in perennial woody plants.