Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, 210014, China.
The Jiangsu Provincial Platform for Conservation and Utilization of Agricultural Germplasm, Nanjing, 210014, China.
Mol Biol Rep. 2020 Nov;47(11):8739-8746. doi: 10.1007/s11033-020-05920-7. Epub 2020 Oct 24.
Stevia rebaudiana Bertoni is an important economic crop that is well known for its secondary metabolites, steviol glycosides (SGs), found in leaves. Because the enzymes of deglycosylation (glycoside hydrolases) play important roles in SGs biosynthetic processes, our study is focused on the functions of β-glucosidases in SGs catabolism in stevia. We cloned and characterized 19 stevia GH1 genes based on transcriptomic sequences. The 19 genes were divided into five putative subfamilies in Arabidopsis. Conserved motifs in the SrGH1 proteins were analysed using the online motif-based sequence analysis tool, MEME. Most of the identified proteins contain the conserved 'TFNEP' motif (contains the catalytic acid/base) and 'ITENG' motif (contains the catalytic nucleophile). Furthermore, the steviol glycoside content and expression of these 19 genes were characterized under constant darkness. The dark treatment lowered the steviol glycoside content significantly, while SrBGLU16 responded to darkness and was markedly upregulated. This study is the first transcriptome-wide analysis of the GH1 family in Stevia rebaudiana. The sequences of 19 SrGH1 members and their expression when grown in darkness were characterized. Among the 19 genes, SrBGLU16 was markedly upregulated by darkness. Thus, we identified SrBGLU16 for further investigation as a possible steviol glycoside beta-glucosidase.
甜菊（Stevia rebaudiana Bertoni）是一种重要的经济作物，以其叶片中含有的次生代谢产物甜菊糖苷（SGs）而闻名。由于糖苷水解酶（糖苷酶）在 SGs 生物合成过程中起着重要作用，我们的研究集中在甜菊中糖苷酶在 SGs 分解代谢中的作用。我们根据转录组序列克隆并鉴定了 19 个甜菊 GH1 基因。这 19 个基因在拟南芥中分为五个假定的亚家族。使用在线基于模体的序列分析工具 MEME 分析 SrGH1 蛋白中的保守模体。大多数鉴定出的蛋白质都含有保守的“TFNEP”模体（包含催化酸碱）和“ITENG”模体（包含催化亲核试剂）。此外，在持续黑暗条件下，对这些 19 个基因的甜菊糖苷含量和表达进行了表征。黑暗处理显著降低了甜菊糖苷的含量，而 SrBGLU16 对黑暗有反应，并显著上调。本研究是对甜菊 GH1 家族的首次全转录组分析。对 19 个 SrGH1 成员的序列及其在黑暗条件下的表达进行了特征描述。在这 19 个基因中，SrBGLU16 被黑暗显著上调。因此，我们确定 SrBGLU16 作为进一步研究的候选基因，可能是一种甜菊糖苷β-葡萄糖苷酶。
