Expression profiling and function analysis highlight the positive involvement of sweet cherry PavTCP17 in regulating flower bud dormancy

Abstract

The TCP transcription factors function diversely in plant growth, development and stress response. The flower bud dormancy was particularly important for the yield formation of fruit trees. However, there has been no in-depth study on the involvement of TCP genes in regulating flower bud dormancy in sweet cherry so far. In the present study, a total of 18 TCP genes were obtained based on the whole genome, which were divided into two subfamilies and three subclasses (PCF, CIN, CYC/TB1) by multiple sequence alignment and evolutionary analysis. Four TCP genes targeted by miR319 were identified in the degradome results. Tissue-specific expression of TCP gene was verified based on transcriptome data and qRT-PCR. The expression patterns of PavTCPs under cold treatment in dormant buds of two cold-requiring sweet cherry cultivars were analyzed, among which PavTCP17 was significantly positively correlated with the gene expressions of gibberellin (GA) degradation and abscisic acid (ABA) synthesis. The abundance of PavTCP17 gene expression was significantly reduced after low cold-requiring cultivars met its chilling demand. The qRT-PCR quantification also showed a decreasing trend of PavTCP17 expression level during blooming process. To further unravel the role of PavTCP17 gene in positively regulating floral bud dormancy, transgenic Arabidopsis overexpressed PavTCP17 was obtained by genetic transformation. Compared with the WT, the number of main branches and rosette leaves was significantly reduced in PavTCP17-overexpressing lines. Moreover, the outgrowth of lateral buds of the PavTCP17-overexpressing lines were remarkably inhibited, mirroring the formation of bud dormancy. Furthermore, PavTCP17 might directly bind to PavNCED3 promoter of sweet cherry, suggesting the implication of PavTCP17 in promoting ABA synthesis, which was essential for bud dormancy. Our study bettered the understanding of TCP gene functions and revealed the mechanism by which PavTCP17 positively regulates flower bud dormancy in sweet cherry.