生长素早期响应基因SAUR对鲜切马铃薯酶促褐变的调控途径

As one of the most important fresh-cut fruits and vegetables, fresh-cut potato is prone to browning during processing, storage and sales, which dramatically decreased its quality and causes enormous economic losses. Therefore, knowing the mechanisms of enzymatic browning of fresh-cut potato is quiet important for controlling the occurrence of browning and maintaining its high quality. Previous research showed that the small auxin up RNA (SAUR) was involved in the regulation of enzymatic browning of fresh-cut potato. Moreover, the enzymatic browning of fresh-cut potato was effectively inhibited by overexpressing the SAUR. The effects of SAUR on regulating the synthesis and transport of auxin was widely reported, however, its effect on regulating the enzymatic browning of fresh-cut fruits and vegetables was rarely reported. Therefore, in order to reveal the pathway of StSAUR regulating the enzymatic browning of fresh-cut potato, this study will be carried out on the basis of previous research. The influence of StSAUR overexpression and silencing on enzymes and substrates involved in enzymatic browning, cell membrane integrity and enzymatic defence system will be investigated. Moreover, the interacting protein of StSAUR will be screened by constructing the yeast hybrid library of potato. The results can provide a theoretical basis for effectively controlling the enzymatic browning of fresh-cut potatoes as well as breeding new varieties of potato which are not easy to browning.

作为鲜切果蔬中最为重要的品类之一，鲜切马铃薯在加工、贮藏及销售过程中极易褐变，严重影响商品价值，造成巨大经济损失。明确其酶促褐变的调控机制，对于控制褐变的发生、提高商品价值具有重要意义。前期研究发现生长素早期响应基因（small auxin up RNA, SAUR）参与调控鲜切马铃薯酶促褐变，且过表达SAUR可有效抑制褐变的发生。SAUR参与调节生长素的合成和运输已有大量报道，但其对鲜切果蔬酶促褐变的调控鲜有报道。因此，在前期研究的基础上，本项目拟综合运用分子生物学、生物化学及生理生化技术，明确马铃薯SAUR基因（StSAUR）过表达和沉默对酶促褐变相关的酶、底物、细胞膜完整性和抗氧化防御体系的影响，并通过构建酵母双杂交文库，筛选出StSAUR的互作蛋白，最终揭示StSAUR对鲜切马铃薯酶促褐变的调控途径。研究结果可为有效控制鲜切马铃薯酶促褐变及培育不易褐变的优良马铃薯品种提供理论依据。

鲜切马铃薯具有营养丰富、干净卫生、食用方便等优点。但鲜切马铃薯在加工、贮藏和销售过程中极易发生酶促褐变，严重影响其商品价值，造成巨大的经济损失。明确其酶促褐变的调控机制，探寻有效的褐变抑制技术，对于控制褐变的发生、提高商品价值具有重要意义。前期研究发现生长素可通过生长素响应基因SAUR对鲜切马铃薯酶促褐变进行调控，但其调控途径尚不明确。基于此，本项目首先对前期的试验进行了补充及验证；然后通过构建StSAUR超表达和纯合突变载体，获得StSAUR超表达和纯合突变的马铃薯植株和块茎，分析了StSAUR对酶促褐变的调控机制；最后通过转录组学筛选到了与StSAUR基因启动子互作的转录因子，最终揭示了其对鲜切马铃薯褐变的调控途径。研究结果表明，生长素主要通过抑制鲜切马铃薯多酚氧化酶（PPO）活性、降低底物酪氨酸和总酚的含量及提高抗氧化能力抑制鲜切马铃薯褐变的发生。通过差异基因和组学分析，证实了生长素响应基因SAUR参与生长素对鲜切马铃薯褐变的调控。利用获得的StSAUR超表达和纯合突变马铃薯块茎进行鲜切试验，发现StSAUR超表达后，马铃薯块茎中PPO活性及基因表达受到抑制，酚类物质含量降低，抗氧化能力提高，褐变程度降低，而stsaur突变块茎呈现相反的结果。通过转录组学分析，发现转录因子MYB能与StSAUR基因启动子互作，且生长素可促进二者的互作。本研究首次揭示了生长素在鲜切马铃薯褐变中的调控机制，并对生长素响应基因StSAUR的功能进行了初步的分析，确定了StSAUR基因在鲜切马铃薯褐变中具有负调控作用，为块茎类蔬菜的酶促褐变精准调控技术提供了重要的理论指导。