Genome-Wide Identification and Expression Analysis of FD Gene Family in Bamboos

The regulation of flowering time is a highly coordinative process that involves the interplay of multiple genes. The FLOWERING LOCUS D (FD) gene is one of those important players. In this study, we identified and characterized FD genes in bamboo, a plant with the unique monocarpy flowering phenomenon. An angiosperm-wide FD gene family analysis demonstrated that unlike the most recent common ancestor (MRCA) of angiosperms, which had only one FD gene, five FD copies were present in the MRCA of Poaceae, and the same gene copy number was retained in the MRCA of the Bambusoideae subfamily. Further analysis of the Poaceae FD gene family revealed five distinctive clades resulted from four duplication events, with two of these events being specific to the Bambusoideae subfamily. High levels of conservation were observed in the gene structure and amino acid composition of structural domain among the FD genes across bamboos and their close relatives, indicating functional conservation. Furthermore, gene expression profiling indicated that FD gene expression in bamboo closely resemble the expression patterns of their homologs in rice. Additionally, overexpression of two bamboo genes (Phy.ed_05093.t1 and Phy.ed_14669.t1) in Arabidopsis resulted in an early flowering phenotype, demonstrating their involvement in the regulation of the flowering process in plants. Our findings provide a comprehensive resource for understanding the evolution, structure, expression, and function of FD genes in Poaceae and Bambusoideae.