Terpene synthases (TPSs) produce a variety of terpenoids that play numerous functional roles in primary and secondary metabolism, as well as in ecological interactions. Here, we report the functional characterization of an inducible potato TPS gene encoding bulnesol/elemol synthase (StBUS/ELS). The expression of StBUS/ELS in potato leaves was significantly induced in response to both bacterial (Pseudomonas syringae) and fungal (Alternaria solani) infection as well as methyl jasmonate treatment, indicating its role in defense. The leaves exhibited the highest StBUS/ELS expression followed by the stem with least and similar expression in tuber, sprout and root. Recombinant StBUS/ELS catalyzed the formation of different sesquiterpenes by utilizing farnesyl diphosphate as substrate, and the monoterpene geraniol from geranyl diphosphate. Among the sesquiterpenes formed by StBUS/ELS, elemol was the predominant product followed by α-bulnesene, bulnesol, and β-elemene. Further GC-MS analysis of StBUS/ELS assay products at different injection temperatures revealed elemol and bulnesol as the major products at 275°C and 200/150°C, respectively, without much change in the levels of minor products. This indicated thermal rearrangement of bulnesol into elemol at higher temperatures. Transient overexpression of StBUS/ELS in potato leaves conferred tolerance against the growth of bacteria P. syringae and Ralstonia solanacearum, and the fungus A. solani. Further, expression analysis of pathogenesis-related (PR) genes in StBUS/ELS overexpressing leaves showed no significant change in comparison to control, indicating a direct involvement of StBUS/ELS enzymatic products against pathogens. Overall, our study suggested that StBUS/ELS is a pathogen-inducible TPS encoding bulnesol/elemol synthase and could provide a direct role in defense against biotic stress in potato.

中文翻译：

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来自马铃薯的防御反应性布尼醇/榄香醇合酶的功能表征

萜烯合酶 (TPS) 产生多种萜类化合物，它们在初级和次级代谢以及生态相互作用中发挥多种功能作用。在这里，我们报告了编码 bulnesol/elemol 合酶 (StBUS/ELS) 的诱导型马铃薯 TPS 基因的功能表征。马铃薯叶片中 StBUS/ELS 的表达在响应细菌（丁香假单胞菌）和真菌（黑链格孢菌）感染以及茉莉酸甲酯处理时显着诱导，表明其在防御中的作用。叶子表现出最高的 StBUS/ELS 表达，其次是茎，块茎、芽和根中表达最少且相似。重组 StBUS/ELS 通过利用法呢基二磷酸作为底物，以及来自香叶基二磷酸的单萜香叶醇催化不同倍半萜的形成。在 StBUS/ELS 形成的倍半萜烯中，elemol 是主要产物，其次是 α-bulnesene、bulnesol 和 β-elemene。在不同注射温度下对 StBUS/ELS 测定产物的进一步 GC-MS 分析显示，elemol 和 bulnesol 分别是 275°C 和 200/150°C 的主要产物，次要产物的水平没有太大变化。这表明在较高温度下布尼醇热重排为elemol。StBUS/ELS 在马铃薯叶片中的瞬时过表达赋予了对丁香假单胞菌和青枯病菌以及真菌 A. solani 生长的耐受性。此外，与对照相比，StBUS/ELS 过表达叶片中发病机制相关 (PR) 基因的表达分析显示没有显着变化，表明 StBUS/ELS 酶产物直接参与对抗病原体。