Overexpression of CpSIZ1 , a SIZ/PIAS-Type SUMO E3 Ligase from Wintersweet ( Chimonanthus praecox ), Delays Flowering, Accelerates Leaf Senescence and Enhances Cold Tolerance in Arabidopsis

Wintersweet ( Chimonanthus praecox L.) is a traditional winter-flowering plant in China and a popular cut flower in winter. Its unique flowering characteristics under cold stress may involve the regulation of a large number of proteins. Protein post-translational modification is an important regulating type for the gene function. However, little is known about the post-translational modification in wintersweet. SUMOylation is an important post-translational modification in eukaryotes. Small ubiquitin-like modifier (SUMO) E3 ligases perform multiple functional regulatory activities in plants via SUMOylation. Here, we cloned and identified a SIZ/PIAS-type SUMO E3 ligase, CpSIZ1 , from wintersweet. CpSIZ1 shared high similarity with other SIZ1 proteins. Quantitative real-time PCR (qRT-PCR) indicated that CpSIZ1 was expressed in all tissues tested, with the highest expression in flower wither period of stage 6, and followed by mature leaves except for different flower development stages. The ectopic expression of CpSIZ1 in Arabidopsis, including the CpSIZ1 overexpression in siz1-2 mutant (HB line) and CpSIZ1 overexpression in WT (OE line), not only promoted vegetative growth, delayed flowering and accelerated leaf senescence, but also improve the cold tolerance in Arabidopsis. Therefore, our studies have enrich the understanding of function of SIZ1 gene in woody plant, and provide a good foundation for further research on the post-translational modification regulation mechanism in this winter-flowering plant.