Molecular cloning and functional characterization of differential genes (PtCCHC and PtMBD6) associated with flowering between precocious trifoliate orange mutant and wild-type trifoliate orange (Poncirus trifoliata L. Raf.)

Flowering is a pivotal developmental event for fruit trees. Most of knowledge about the molecular regulatory mechanisms of flowering regulation comes from studies in model plants. However, knowledge on the regulation of the floral transition from vegetative growth in perennial fruit species is limited. Citrus is an evergreen perennial fruit tree genus with a complex genetic background. In this study, a total of 27 genes with sequence differences between precocious trifoliate orange and wild -type trifoliate orange were identified based on data from a previous study. qRT-PCR result showed that two candidate genes, PtCCHC and PtMBD6, were differentially expressed between precocious trifoliate orange and wild -type. Moreover, PtCCHC was highly expressed, whereas PtMBD was expressed low at the early flowering stage in precocious trifoliate orange. Overexpression of PtCCHC in Arabidopsis resulted in early flowering and overexpression of PtMBD6 in Arabidopsis resulted in late flowering. We also found that silencing PtMBD6 can reduce the expression of PtFT in Citrus lemon. This study will provide valuable insights for future studies in citrus flowering.