MYB转录因子调控采后火龙果果实糖代谢的机制解析

Sugar content is an important indicator of fruit quality. Pitaya is one of the special fruits rapidly developed in recent years. However, the sugar content of postharvest pitaya in storage and transportation process is dramatically declined, which reduces the quality of the fruits. It has been reported that MYB transcription factor plays an important regulatory role in the formation of fruit quality. However, it has not been studied whether MYB transcription factor is involved in regulating sugar metabolism and its specific mechanism in postharvest pitaya fruit. In this project, on the basis of pitaya, the key enzyme genes for sugar metabolism in postharvest pitaya fruit are screened and identified by RNA-seq and qRT-PCR, and then its promoter is isolated. MYB transcription factors directly bonding the key enzyme gene promoter for sugar metabolism and interaction proteins of MYB are defined through DNA-protein interaction, protein-protein interaction and other technologies. Moreover, the influence of interaction proteins in downstream target genes regulated by MYB transcription factors is analyzed, thus the transcriptional regulation mechanism of MYB transcription factors regulating sugar metabolism in postharvest pitaya is investigated. The research results not only deepen the understanding of the transcriptional regulation mechanism of sugar metabolism in postharvest fruits, but also provide a new theoretical basis for improving the preservation technology of fruit quality of postharvest pitaya.

糖含量是影响果实品质的一项重要指标。火龙果是近几年快速发展的特色水果之一，但采后火龙果果实贮运过程糖含量明显下降，降低了果实的商品品质。已有报道表明MYB转录因子在果实品质形成中发挥重要的调控作用，但MYB转录因子是否参与调控采后火龙果果实糖代谢及其具体机制，目前未见相关研究。基于RNA-seq表达谱和实时荧光定量，本项目首先筛选确定参与采后火龙果果实糖代谢关键酶类基因，进而分离其启动子；进一步通过DNA-蛋白质互作技术，筛选、鉴定直接结合糖代谢关键酶类基因启动子的MYB转录因子；采用蛋白质互作技术，筛选、鉴定MYB的互作蛋白，并分析其对MYB调控下游靶基因的影响，进而系统解析MYB转录因子调控采后火龙果果实糖代谢的分子机制。研究结果将加深对采后果实糖代谢的转录调控机制的认识，也可为改进维持火龙果果实采后品质的保鲜技术措施提供新的理论依据。

贵州火龙果种植面积达13多万亩，成为全国火龙果种植面积大省之一，种植面积广、产量高，随着消费者对果实高品质的需求，深入研究采后果实品质具有重要意义。为了实现火龙果采后高品质贮藏要求，本项目研究了不同保鲜处理（热处理、自发气调包装、褪黑素等）可以有效抑制采后贮藏期果实糖代谢的消耗与分解，保持果实较高地糖含量，从而延缓果实的衰老进程；测定糖代谢途径酶（蔗糖磷酸合成酶、蔗糖合成酶和转化酶）在果实衰老过程中酶活性的变化情况，得出随着果实衰老程度的增加，糖代谢途径酶酶活性逐渐降低，且筛选出糖代谢途径相关酶基因（HpSPS1、HpINV1、HpINV2、HpSuSy1）的表达随着衰老程度的增加而降低；通过DNA-蛋白质技术筛选、鉴定糖代谢途径关键酶基因的上游转录调控因子HpMYB56，并对HpMYB56的分子特性以及对糖代谢基因的调控能力进行解析；通过蛋白质-蛋白质互作技术筛选、鉴定HpMYB56的互作蛋白HpWRKY3，并对HpWRKY3的分子特性以及对糖代谢基因的调控能力进行解析。上述研究结果阐明了火龙果采后贮藏期糖代谢的变化规律，筛选了糖代谢途径的关键基因，解析了HpMYB56以及互作蛋白HpWRKY3对糖代谢途径基因的转录调控。本项目的研究结果丰富和加深了人们对火龙果果实糖代谢变化规律以及MYB转录因子参与果实糖代谢调控的网络机制的认识，为改进维持火龙果果实采后品质的保鲜技术措施提供新的理论依据，同时对开展贵州喀斯特山区火龙果种质资源筛选、发掘与利用，推进贵州优质火龙果产业化，都有着十分重要的意义。在本项目的资助下，已经在《International Journal of Molecular Sciences》《Food Science and Technology》、《中国南方果树》、《食品研究与开发》、《食品科技》、《中国果树》、《现代食品科技》等刊物上发表9篇学术论文。项目负责人巴良杰获得2020年贵阳市高层次创新型青年科技人才、2021年贵州省高层次创新型人才（“千层次”）。