State Key Laboratory for Efficient Production of Forest Resources, Key Laboratory of Silviculture and Conservation of the Ministry of Education, Ministry of Education of Engineering Research Centre for Forest and Grassland Carbon Sequestration, College of Forestry, Beijing Forestry University, P. O. Box 407, No.35 Qinghua East Road, Haidian District, Beijing, 100083, China.
College of Forestry, Guangxi University, Nanning, 530004, China.
BMC Plant Biol. 2024 Jun 21;24(1):588. doi: 10.1186/s12870-024-05281-4.
Soapberry (Sapindus mukorossi) is an economically important multifunctional tree species. Triterpenoid saponins have many functions in soapberry. However, the types of uridine diphosphate (UDP) glucosyltransferases (UGTs) involved in the synthesis of triterpenoid saponins in soapberry have not been clarified.
In this study, 42 SmUGTs were identified in soapberry, which were unevenly distributed on 12 chromosomes and had sequence lengths of 450 bp to 1638 bp, with an average of 1388 bp. The number of amino acids in SmUGTs was 149 to 545, with an average of 462. Most SmUGTs were acidic and hydrophilic unstable proteins, and their secondary structures were mainly α-helices and random coils. All had conserved UDPGT and PSPG-box domains. Phylogenetic analysis divided them into four subclasses, which glycosylated different carbon atoms. Prediction of cis-acting elements suggested roles of SmUGTs in plant development and responses to environmental stresses. The expression patterns of SmUGTs differed according to the developmental stage of fruits, as determined by transcriptomics and RT-qPCR. Co-expression network analysis of SmUGTs and related genes/transcription factors in the triterpenoid saponin synthesis pathway was also performed. The results indicated potential roles for many transcription factors, such as SmERFs, SmGATAs and SmMYBs. A correlation analysis showed that 42 SmUGTs were crucial in saponin synthesis in soapberry.
Our findings suggest optimal targets for manipulating glycosylation in soapberry triterpenoid saponin biosynthesis; they also provide a theoretical foundation for further evaluation of the functions of SmUGTs and analyses of their biosynthetic mechanisms.
无患子是一种具有重要经济价值的多功能树种。三萜皂苷在无患子中具有多种功能。然而，无患子中参与三萜皂苷合成的尿苷二磷酸（UDP）葡萄糖基转移酶（UGTs）的类型尚未阐明。
本研究在无患子中鉴定出 42 个 SmUGTs，它们不均匀地分布在 12 条染色体上，序列长度为 450bp 至 1638bp，平均为 1388bp。SmUGTs 的氨基酸数为 149 至 545，平均为 462。大多数 SmUGTs 是酸性和亲水不稳定的蛋白质，其二级结构主要为α-螺旋和无规卷曲。它们都具有保守的 UDPGT 和 PSPG 盒结构域。系统发育分析将它们分为四个亚类，这些亚类糖基化了不同的碳原子。顺式作用元件的预测表明 SmUGTs 在植物发育和对环境胁迫的响应中起作用。通过转录组学和 RT-qPCR 确定，SmUGTs 的表达模式根据果实的发育阶段而不同。还对三萜皂苷合成途径中的 SmUGTs 及其相关基因/转录因子的共表达网络进行了分析。结果表明，许多转录因子（如 SmERFs、SmGATAs 和 SmMYBs）可能具有重要作用。相关性分析表明，42 个 SmUGTs 在无患子皂苷合成中至关重要。
我们的研究结果为在无患子三萜皂苷生物合成中操纵糖基化提供了最佳靶点；它们还为进一步评估 SmUGTs 的功能和分析其生物合成机制提供了理论基础。
