桂花 OfNCED3 调控转基因烟草叶片类胡萝卜素和叶绿素的合成

In this study，the OfNCED3 cDNA sequence were acquired based on the transcriptional data of Osmanthus fragrans ‘Yanhong Gui’. The multiple sequence alignment analysis showed that OfNCED3 had two conservative domain（MIAHPKxDP and HDFAITE）characteristics of the NCED family and four conserved histidine residues. Phylogenetic analysis indicated that OfNCED3 is grouped together with SlNCED1. The results of real-time quantitative PCR showed that the expression of OfNCED3 in the petals of‘Yanhong Gui’with higher carotenoid content was significantly lower than that of‘Yu Linglong’with lower carotenoid content during flower opening process. It is speculated that OfNCED3 may be related to the difference of carotenoid contents between‘Yanhong Gui’and‘Yu Linglong’petals. Transgenic tobacco lines overexpressing OfNCED3 were obtained by an Agrobacterium-mediated method. The contents of chlorophyll，carotenoid and ABA were determined by using spectrophotometer and ultra high performance liquid chromatography（UPLC），and the expression levels of genes related to carotenoid pathway were analyzed via real-time quantitative PCR. The overexpression of OfNCED3 gene expression resulted in a significant decrease of chlorophyll and carotenoid contents and a increase of endogenous ABA content. The expression of carotenoid synthesis genes was significantly up-regulated，and the downstream synthesis genes were more up-regulated than the upstream synthesis genes. This research suggests OfNCED3 can promote the synthesis of ABA by degrading carotenoids in plants.