Genome-wide identification of the gene family in and its homologs expression patterns during flower development in different species.

TCP proteins, part of the transcription factors specific to plants, are recognized for their involvement in various aspects of plant growth and development. Nevertheless, a thorough investigation of in , a prominent ancestral species of cultivated chrysanthemum and an excellent model material for investigating ray floret (RF) and disc floret (DF) development in , remains unexplored yet. Herein, a comprehensive study was performed to analyze the genome-wide distribution of in . In total, 39 in were identified, showing uneven distribution on 8 chromosomes. Phylogenetic and gene structural analyses revealed that were grouped into classes I and II. The class II genes were subdivided into two subclades, the CIN and CYC/TB1 subclades, with members of each clade having similar conserved motifs and gene structures. Four CIN subclade genes (, , , and ) contained the potential miR319 target sites. Promoter analysis revealed that had numerous -regulatory elements associated with phytohormone responses, stress responses, and plant growth/development. The expression patterns of during capitulum development and in two different florets were determined using RNA-seq and qRT-PCR. The expression levels of s varied in six development stages of capitula; 25 out of the 36 genes were specifically expressed in flowers. Additionally, we identified six key genes, which belong to the class II TCP subclade, with markedly upregulated expression in RFs compared with DFs, and these genes exhibited similar expression patterns in the two florets of species. It is speculated that they may be responsible for RFs and DFs development. Subcellular localization and transactivation activity analyses of six candidate genes demonstrated that all of them were localized in the nucleus, while three exhibited self-activation activities. This research provided a better understanding of in and laid a foundation for unraveling the mechanism by which important involved in the capitulum development.