红皮西洋梨果皮红色消退的分子机理研究

Red-skin pear is a hotspot of current pear development. As one of an important red-skin pear cultivars,‘Max Red Bartlett’ is welcomed by consumers for its excellent quality. However, the color-fading of ‘Max Red Bartlett’ fruit peel in late fruit developmental stage greatly limit its economic value. Anthocyanin is basis of red-color of fruit peel. In later fruit developmental stage, the content of anthocyanin is reduced rapidly, so we speculated that the color-fading of ‘Max Red Bartlett’ is related to the synthesis and degradation of anthocyanin. This study will analyze this problem systematically. With ‘Red clap＇s’ pear as a control , we will first analysis the anthocyanin synthesis and degradation rate in different fruit development of ‘Max Red Bartlett’, and find the reason for abnormal coloration of ‘Max Red Bartlett’in physiological level; To screening the genes which may related to color-fading, the transcriptome and anthocyanin biosynthesis genes expression in different fruit development stage of ‘Max Red Bartlett’ and ‘Red clap＇s’ will be performed. And finally we will obtain several genes which related to color-fading of ‘Max Red Bartlett’; these genes will also be verified by Northern Blot, gene transient expression technology. Through the biology functional analysis, we will screen the key genes which regulate the color-fading of ‘Max Red Bartlett’, and clarify the molecular mechanism of color-fading of ‘Max Red Bartlett’ preliminary. This study will lay the foundation for discovering the coloring molecular mechanism of Red-skin pear and provide reference and theoretical support for the Red-skin pear breeding.

红皮西洋梨由于其优良品质深受消费者喜爱，但成熟果实果皮红色消退问题严重影响了其商品价值。花青苷是红色果皮形成的物质基础，前期研究发现红皮西洋梨品种‘红巴梨’果实发育后期花青苷含量降低，因此推测其果皮红色消退与花青苷合成和降解有关。本项目将在此基础上，首先测定‘红巴梨’和‘红星’果实发育各阶段花青苷的含量，分析对比其合成和降解速率变化；检测‘红巴梨’果实中花青苷合成相关结构和调控基因在发育各阶段的表达变化，并与对照‘红星’梨进行比较，筛选与‘红巴梨’褪色有关的基因；分析‘红巴梨’果实发育期果皮转录组，对比‘红星’转录组测序结果并筛选出新的可能参与果皮红色消退的基因；最后，通过Northern Blot、基因瞬时表达等实验最终确定‘红巴梨’红色消退的关键基因。本研究将为红皮梨分子改良和着色机理研究奠定基础，并为红皮梨的良种选育提供参考和理论支撑。

‘红巴梨’是国内重要的红皮西洋梨主栽品种之一，然而果皮在果实发育后期红色褪色问题严重影响到‘红巴梨’果实的经济价值，并成为制约‘红巴梨’产业发展的重要因素。本研究通过红皮梨品种果实发育期花青苷含量分析，初步确定“红巴梨”果实发育后期果皮红色消退是由花青苷含量显著减少引起，主要原因是果实发育后期花青苷合成速率减少与花青苷降解速率增加的综合作用；“红星”不存在褪色现象，主要原因是果实发育后期花青苷合成速率高于或持平与花青苷降解速率。通过转录组分析，获得可能与“红巴梨”果实发育后期果皮红色消退密切相关的候选基因：LDOX、FLS、GST、POD、MYBs和bHLHs等。通过瞬时表达分析，初步证实MYB44、MYB108和GST等与花青苷含量累积存在正相关关系。而POD基因过表达抑制花青苷积累。通过综合分析，“红巴梨”果实发育后期果皮红色消退不是由单一因素造成，是多因素控制的结果（花青苷-合成减少、降解增加、转运受阻，诸多转录因子复杂调控）。最终推测出‘红巴梨’果皮发育后期褪色基因调控模型。此外，本项目还对不同着色类型红皮梨的主效基因进行分析，6个不同的红皮梨品种，主要可以分为3种不同类型。第一种是红早酥和红蓓蕾莎，花青苷含量主要受到主成分（PAC）1的影响；第二种主要是红丝绸和红星，花青苷含量主要受到主成分2的影响； 第三种是5号优系、红巴梨，受到两种主成分的影响。决定PCA1的基因是PAL、F3H、CHS、CHI、DFR1、ANS、UFGT2、bHLH3、MYB10、ELIP1。决定PAC2的基因是ANR、UFGT1、MYB10b、COP1。决定两种主成分的基因是bHLH3、GST、COP1.1。