采后枇杷果实冷害木质化的HSF转录调控分子机制研究

Loquat (Eriobotrya japonica Lindl.), a subtropical exotic fruit originated from China, belongs to chilling sensitive fruit. It develops flesh lignification with deterioration of fruit qualities such as browning and rot during long term cold storage. The present project will focus on regulation of transcription factor HSF in chilling injury induced flesh lignification, which is based on our decade's study on postharvest loquat fruit. Co-expression of EjHSF genes and molecular chaperone EjHSP genes in relation to lignin biosynthesis will be investigated for identification of key EjHSF gene(s) and its (their) target gene(s) involved in lignin biosynthesis. Further regulation mechanism of EjHSF(s) and their target gene(s) will be studied by yeast hybrid system and dual-luciferase system, and confirmed by transient assay and transgenic study. The results of the present project will provide new targets for manipulation of loquat fruit chilling injury induced lignification and provide new evidence for improving postharvest technology of the loquat industry.

枇杷为原产我国的特色水果，属冷敏果实，采后冷藏过程中易出现冷害木质化，并伴随着品质劣变，商品性迅速丧失。本项目拟在前期研究基础上，深入研究转录因子HSF家族成员对枇杷冷害木质化的调控，通过协同表达模式分析确定参与冷害木质素代谢调控的EjHSF候选基因，采用双荧光素酶体系、酵母杂交技术、瞬时表达和转基因等手段明确并验证受EjHSF转录调控的木质素代谢相关靶标基因关键成员及EjHSP成员，阐明不同采后处理条件下EjHSF转录调控枇杷果实冷害木质化的分子机制，为利用生物技术手段调控果实冷害等品质劣变提供新靶标，并为改善枇杷果实采后技术体系提供新依据。

项目开展了枇杷果实采后冷害木质化的调控方式与相关基因表达，探索了采后枇杷果实冷害木质化的HSF转录调控分子机制。结果表明：热激处理（HT）和程序降温处理（LTC）可以显著减轻采后枇杷冷害木质化及其引起的硬度升高；从‘洛阳青’（LYQ）果实 中克隆得到了3个热响应因子（EjHSF1、EjHSF2和EjHSF3）和8个热激蛋白基因（EjHsp70-1/2、EjsHsp1/2/3/4/5/6），它们在不同组织和发育阶段广泛表达。HT和LTC处理能通过诱导EjHSF基因的表达提高枇杷果实耐冷性。EjHSF1响应HT处理，并且能够通过转录调控HSP基因参与枇杷果实冷害。EjHSF3不响应HT处理，但受到LTC处理抑制，并与果肉木质化呈正相关关系。EjHSF3通过转录调控木质素生物合成基因及与EjAP2-1转录因子蛋白互作来参与调控枇杷果肉木质化。因此，EjHSF转录因子通过两条不同的途径参与调控枇杷果实冷害木质化。研究结果丰富了果实采后木质化的生物学理论，也为完善果实贮运体系提供了科技支撑。