低温是限制茶树正常生长以及地理分布的主要因素。包括低温胁迫在内的非生物胁迫会造成活性氧（ROS）积累进而对植物细胞产生毒害作用，大量研究表明诱导清除ROS的细胞抗氧化机制对保护机体免受各种胁迫尤为重要。萜烯类是植物中数量最多的一类香气组分，主要包括单萜类和倍半萜类等，其中橙花叔醇是存在最广泛的一类倍半萜烯类物质，它除了产生花香外，还具有包括抗氧化在内的生物活性。糖基化作用是由UGP-糖基转移酶（UGT）催化的活化的核苷酸糖转移到受体苷元形成糖苷的过程，对植物的生长发育以及响应生物和非生物胁迫具有关键作用。有研究表明冻害胁迫下茶树中的橙花叔醇的含量是上升的，因此作者假设作为橙花叔醇储存形式的橙花叔醇糖苷在低温下也是积累的。在本研究中，作者从茶树的298个UGT基因中通过低温下转录水平与橙花叔醇糖苷含量的相关性分析筛选到6个显著相关的UGT基因，进一步将低温下显著诱导表达的两个基因作为介导橙花叔醇糖苷化的候选基因。接着酶活性分析显示只有候选基因UGT91Q2能够在以橙花叔醇为底物生成相应的糖苷，因此后续重点对该基因进行了功能分析，结果揭示了橙花叔醇糖基化在茶树冷胁迫响应中的特殊作用。

Abstract

Plants produce and emit terpenes, including sesquiterpenes, during growth and development, which serve different functions in plants. The sesquiterpene nerolidol has health‐promoting properties and adds a floral scent to plants. However, the glycosylation mechanism of nerolidol and its biological roles in plants remained unknown.

Sesquiterpene UDP‐glucosyltransferases were selected by using metabolites‐genes correlation analysis, and its roles in response to cold stress were studied.

We discovered the first plant UGT (UGT91Q2) in tea plant, whose expression is strongly induced by cold stress and which specifically catalyzes the glucosylation of nerolidol. The accumulation of nerolidol glucoside was consistent with the expression level of UGT91Q2 in response to cold stress, as well as in different tea cultivars. The reactive oxygen species (ROS) scavenging capacity of nerolidol glucoside was significantly higher than that of free nerolidol. Down‐regulation of UGT91Q2 resulted in reduced accumulation of nerolidol glucoside, ROS scavenging capacity and tea plant cold tolerance. Tea plants absorbed airborne nerolidol and converted it to its glucoside, subsequently enhancing tea plant cold stress tolerance.

Nerolidol plays a role in response to cold stress as well as in triggering plant‐plant communication in response to cold stress. Our findings reveal previously unidentified roles of volatiles in response to abiotic stress in plants.