Open Access

ARTICLE

Selenium Regulates Antioxidant Capacities and Diterpenoid Biosynthesis in the Medicinal Plant Isodon rubescens

Fenglan Zhao^1,2,#, Shuwen Wu^1,#, Xue Meng¹, Jianping Xue^1,2, Yongbo Duan^1,2,*
1 Anhui Provincial Engineering Laboratory for Efficient Utilization of Featured Resource Plants, College of Life Sciences, Huaibei Normal University, Huaibei, 235000, China
2 Huaibei Key Laboratory of Efficient Cultivation and Utilization of Resource Plants, College of Life Sciences, Huaibei Normal University, Huaibei, 235000, China
* Corresponding Author: Yongbo Duan. Email:

Phyton-International Journal of Experimental Botany https://doi.org/10.32604/phyton.2024.052287

Received 28 March 2024; Accepted 11 June 2024; Published online 10 July 2024

Abstract

Dōng líng căo, the dried aboveground parts of Isodon rubescens (Hemls.) Hara., is commonly consumed as a medicinal decoction or tea beverage. Natural beverages can be an important source of human dietary selenium (Se). However, how I. rubescens plants respond to exogenous Se remains unknown. In this study, a pot cultivation experiment was employed to investigate the phenotypic and physiological responses of I. rubescens plants exposed to Se. Fifteen days after applying different concentrations of sodium selenate to the soil, the Se enrichment capacity, growth indices, antioxidant capacities, and the content of flavonoids and diterpenoids were measured in the plants. Further, the oridonin content was quantified using the high-performance liquid chromatography method, and the expression levels of key diterpenoid synthesis genes were analyzed by quantitative real-time PCR (qRT-PCR). I. rubescens plants efficiently accumulated Se, with the Se content increasing proportionally to the applied dose, reaching levels of nearly 200 mg·kg dry leaves as Se concentration increased. None of the three Se treatments significantly altered the phenotypic indices, except a longer root length occurred in the 3 μM·kg Se group. Among three Se doses, 6 μM·kg Se gave the highest accumulation of flavonoids, diterpenoids, and oridonin, with the increase of 2.0-, 1.8-, and 1.9-fold in aboveground parts, respectively. Selenium application boosted the activities of antioxidant enzymes and antioxidant capacities according to 2,2-Diphenyl-1-picrylhydrazyl (DPPH), ferric reducing/antioxidant power, and tea brewing color experiments. Four key synthase genes were upregulated significantly by 6 μM·kg Se treatment, notably 1-deoxy-D-xylulose 5-phosphate reductoisomerase (IrDXR), with a 5-fold increase, and kaurene synthase-like 4 (IrKSL4), with a 6-fold increase. Thus, Se application in I. rubescens cultivation may be a potential biofortification method to supplement Se while increasing flavonoid and diterpenoid contents.

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Keywords

Flavonoids; oridonin; physiological indicators; quantitative real-time PCR; selenium

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