糖信号调控牡丹切花花青素苷合成的分子机理研究

Anthocyanins are responsible for the different colors in petals. Reports have detailed the regulation of a complex array of outside signals in anthocyanin biosynthetic pathway. Sugars act as the primary hormone-like signals in plants and are involved in the regulation of anthocyanin biosynthetic pathway as signaling molecules. Tree peony cut flowers are not able to develop flower color normally during postharvest process,which has a negetive influence on both ornamental and business value.In order to figure out the molecular mechanism of sugars regulating anthocyanin biosynthesis in tree peony (Paeonia suffruticosa) cut flowers and understand the fundamental reason of their postharvest color distortion , cultivars with different anthocyanin composition will be employed as materials in this project for analyzing the effect of sugars on petal color quality and anthocyanin accumulation, the regulation mechanism between anthocyanin biosynthetic regulatory genes and structural genes, the sugar-signal-regulated expression of genes involved in anthocyanin biosynthesis and HXK genes involved in sugar signal sensing and transduction, and the biological function of HXK genes of tree peony. Not only will this research provide theoretical reference for the postharvest technology development of tree peony cut flower, promote the understanding of the molecular mechanism of tree peony flower color development, but also post theoretical foundations for the future selective coloring cultivars breeding of tree peony based on the genetic modification.

花青素苷是决定观赏植物花瓣呈现不同颜色的重要色素类型之一，而外界信号对花青素苷合成途径具有调控作用。糖在植物体内具有类似植物激素的初级信使作用，因而有可能调控花青素苷合成。离体的牡丹切花采后花色不能正常发育，影响其观赏和商业价值。项目选择花青素苷组成不同的牡丹品种为试材，研究糖对其切花花色品质和花青素苷积累的影响、花青素苷合成途径相关调节基因与结构基因的调控关系、糖信号对花青素苷合成途径相关基因及糖信号感知和转导基因HXK的转录调控作用、HXK基因的生物学功能，以期明晰糖调控牡丹切花花青素苷合成的分子机理，进而理解其采后花色失真的根本原因。研究成果将不仅为牡丹切花采后保鲜技术的开发提供理论依据，而且有助于解析牡丹花色形成的分子机制，为利用现代分子生物学手段对牡丹进行基因改良从而培育更高观赏和商业价值的切花品种奠定理论基础。

本研究以不同花青素苷组分牡丹品种‘洛阳红’和‘太阳’为研究对象，进行葡萄糖、葡萄糖类似物及己糖激酶抑制剂处理，结果发现葡萄糖可通过信号途径促进Cy3G5G、Cy3G、Pn3G、Pn3G5G、Pg3G5G和Pg3G花青素组分的合成，提高切花花色品质。利用已获得的‘洛阳红’牡丹花瓣转录组数据库，获得了花青素苷合成相关7个调节基因和8个结构基因全长序列，其中调节基因PsWD40-2、PsMYB2和结构基因PsCHS1、PsCHI1、PsF3′H1、Ps3GT1和PsOMT1响应葡萄糖信号调控。推测葡萄糖信号通过不依赖HXK途径调控PsWD40-2、PsMYB2、PsCHS1和PsCHI1基因的表达，通过依赖HXK途径调控PsF3′H1、Ps3GT1和PsOMT1基因的表达。研究克隆出牡丹花青素苷合成关键结构基因PsF3′H1的启动子序列，长1457bp，其启动子序列中含有多个与MYB和光诱导相关的顺势作用原件，除此还含有响应多种激素诱导调控作用位点，推测PsF3′H1可能是受上游MYB转录因子的调控，进而响应葡萄糖信号，同时PsF3′H1也可能是通过参与激素信号调控，进而响应葡萄糖信号。此外，从牡丹中分离得到葡萄糖信号感知和转导关键因子HXK的2个同源基因PsHXK1和PsHXK2的cDNA全长。依据序列分析和系统进化树分析，推测PsHXK1和PsHXK2蛋白均具有催化己糖磷酸化的功能。根据牡丹‘洛阳红’花瓣中PsHXK1和PsHXK2基因表达情况，推测这2个基因的转录水平可能与己糖含量有密切的关联。通过PsHXK1和PsHXK2基因过表达转化拟南芥的研究发现，PsHXK1和PsHXK2具备糖信号感知和转导的功能，可以响应高浓度葡萄糖调控花青素苷合成相关基因的表达，提高转基因拟南芥的花青素苷含量。