Abstract
Chilling has a critical role in the growth and development of perennial plants. The chilling requirement (CR) for dormancy breaking largely depends on the species. However, global warming is expected to negatively affect chilling accumulation and dormancy release in a wide range of perennial plants. Here, we used Chimonanthus praecox as a model to investigate the CR for dormancy breaking under natural and artificial conditions. We determined the minimum CR (570 chill units, CU) needed for chilling-induced dormancy breaking and analyzed the transcriptomes and proteomes of flowering and non-flowering flower buds (FBs, anther and ovary differentiation completed) with different CRs. The concentrations of ABA and GA3 in the FBs were also determined using HPLC. The results indicate that chilling induced an upregulation of ABA levels and significant downregulation of SHORT VEGETATIVE PHASE (SVP) and FLOWERING LOCUS T (FT) homologs at the transcript level in FBs when the accumulated CR reached 570 CU (IB570) compared to FBs in November (FB.Nov, CK) and nF16 (non-flowering FBs after treatment at 16 °C for -300 CU), which suggested that dormancy breaking of FBs could be regulated by the ABA-mediated SVP-FT module. Overexpression in Arabidopsis was used to confirm the function of candidate genes, and early flowering was induced in 35S::CpFT1 transgenic lines. Our data provide insight into the minimum CR (570 CU) needed for chilling-induced dormancy breaking and its underlying regulatory mechanism in C. praecox, which provides a new tool for the artificial regulation of flowering time and a rich gene resource for controlling chilling-induced blooming.