Liu Juan, Wang Jiaxue, Chen Mingjia, Meng Wenna, Ding Anping, Chen Miao, Ding Rongping, Tan Mingpu, Xiang Zengxu
College of Life Sciences, State Key Laboratory of Crop Genetics & Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, China.
College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China.
Plants (Basel). 2024 Sep 10;13(18):2542. doi: 10.3390/plants13182542.
(Bertoni) is a valuable sweetener plant whose sweetness primarily derives from steviol glycosides (SGs), especially rebaudioside A (RA). Polyploidization has the potential to enhance the content of active ingredients in medicinal plants, making this strategy a promising avenue for genetic improvement. However, the underlying regulatory mechanisms that contribute to the fluctuating SGs content between autotetraploid and diploid stevia remain unclear. In this study, we employed metabolic analysis to identify 916 differentially accumulated metabolites (DAMs), with the majority, specifically terpenoids, flavonoids, and lipids, exhibiting upregulation due to polyploidization. Notably, the content of stevia's signature metabolite SGs (including RA, steviolbioside, and rebaudioside C), along with their precursor steviol, increased significantly after polyploidization. Furthermore, a comprehensive analysis of the transcriptome and metabolome revealed that the majority of differentially expressed genes (DEGs) involved in the SG-synthesis pathway (, , , , , , and ) were upregulated in autotetraploid stevia, and these DEGs exhibited a positive correlation with the polyploidization-enhanced SGs. Additionally, multi-omics network analysis indicated that several transcription factor families (such as five , four , three , eight , and three ), various transporter genes (four ABC transporters, three triose-phosphate transporters, and two sugar efflux transporters for intercellular exchange), as well as microorganisms (including and ) were positively correlated with the accumulation of RA and steviol. Overall, our results indicate the presence of a regulatory circuit orchestrated by polyploidization, which recruits beneficial rhizosphere microbes and modulates the expression of genes associated with SG biosynthesis, ultimately enhancing the SG content in stevia. This finding will provide new insights for promoting the propagation and industrial development of stevia.
甜叶菊是一种珍贵的甜味剂植物，其甜味主要源于甜菊糖苷（SGs），尤其是莱鲍迪苷A（RA）。多倍体化有潜力提高药用植物中活性成分的含量，使这一策略成为有前景的遗传改良途径。然而，导致同源四倍体和二倍体甜叶菊之间SGs含量波动的潜在调控机制仍不清楚。在本研究中，我们采用代谢分析鉴定出916种差异积累代谢物（DAMs），其中大多数，特别是萜类、黄酮类和脂质，因多倍体化而呈上调。值得注意的是，甜叶菊标志性代谢物SGs（包括RA、甜菊糖苷和莱鲍迪苷C）及其前体甜菊醇的含量在多倍体化后显著增加。此外，对转录组和代谢组的综合分析表明，参与SG合成途径（，，，，，，和）的大多数差异表达基因（DEGs）在同源四倍体甜叶菊中上调，并且这些DEGs与多倍体化增强的SGs呈正相关。此外，多组学网络分析表明，几个转录因子家族（如五个，四个，三个，八个和三个）、各种转运蛋白基因（四个ABC转运蛋白、三个磷酸丙糖转运蛋白和两个用于细胞间交换的糖外排转运蛋白）以及微生物（包括和）与RA和甜菊醇的积累呈正相关。总体而言，我们的结果表明存在由多倍体化精心编排的调控回路，该回路招募有益的根际微生物并调节与SG生物合成相关的基因表达，最终提高甜叶菊中SG的含量。这一发现将为促进甜叶菊的繁殖和产业发展提供新的见解。
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