UV-B Radiation Largely Promoted the Transformation of Primary Metabolites to Phenols in Astragalus mongholicus Seedlings.

Li-Qiang Mu,Ann Abozeid,Yang Liu,Zhong-Hua Tang,Ke-Xin Wu,Jia Liu,Xiao-Rui Guo

doi:10.3390/biom10040504

Li-Qiang Mu, Ann Abozeid + Show 5 more

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https://doi.org/10.3390/biom10040504

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Journal: Biomolecules	Publication Date: Mar 26, 2020
Citations: 25	License type: CC BY 4.0

Affiliation: Northeast Forestry University, Menoufia University

Abstract

Ultraviolet-B (UV-B) radiation (280–320 nm) may induce photobiological stress in plants, activate the plant defense system, and induce changes of metabolites. In our previous work, we found that between the two Astragalus varieties prescribed by the Chinese Pharmacopoeia, Astragalus mongholicus has better tolerance to UV-B. Thus, it is necessary to study the metabolic strategy of Astragalus under UV-B radiation further. In the present study, we used untargeted gas chromatography-mass spectrometry (GC-MS) and targeted liquid chromatography-mass spectrometry (LC-MS techniques) to investigate the profiles of primary and secondary metabolic. The profiles revealed the metabolic response of Astragalus to UV-B radiation. We then used real-time polymerase chain reaction (RT-PCR) to obtain the transcription level of relevant genes under UV-B radiation (UV-B supplemented in the field, λmax = 313 nm, 30 W, lamp-leaf distance = 60 cm, 40 min·day−1), which annotated the responsive mechanism of phenolic metabolism in roots. Our results indicated that supplemental UV-B radiation induced a stronger shift from carbon assimilation to carbon accumulation. The flux through the phenylpropanoids pathway increased due to the mobilization of carbon reserves. The response of metabolism was observed to be significantly tissue-specific upon the UV-B radiation treatment. Among phenolic compounds, C6C1 carbon compounds (phenolic acids in leaves) and C6C3C6 carbon compounds (flavones in leaves and isoflavones in roots) increased at the expense of C6C3 carbon compounds. Verification experiments show that the response of phenolics in roots to UV-B is activated by upregulation of relevant genes rather than phenylalanine. Overall, this study reveals the tissues-specific alteration and mechanism of primary and secondary metabolic strategy in response to UV-B radiation.

Highlights

Astragalus mongholicus (A. mongholicus) is an important perennial herb of the Legumes family [1,2]
To deeply explore the response and mechanism explaining how metabolic reprogramming can achieve a new steady state under increased UV-B radiation, we investigated the influence on the specific tissue accumulation of primary and phenolic metabolites using untargeted (GC-MS) and targeted (LC-MS) metabolomics in A. mongholicus under increased UV-B radiation
The effect of UV-B radiation on morphology can be seen in Figure 1 and Table 2

Summary

Introduction

Astragalus mongholicus (A. mongholicus) is an important perennial herb of the Legumes family [1,2]. The most common protective mechanism against potentially damaging irradiation is the biosynthesis of UV-absorbing compounds [16] These secondary metabolites mostly consist of phenolic compounds, flavonoids, and hydroxycinnamate esters, which accumulate in the vacuoles of epidermal cells in response to UV-B radiation and attenuate the penetration of the UV-B portion of the solar spectrum into deeper cell layers with little effect on the visible region. These responses to UV-B radiation may result in the reprogramming of metabolites in A. mongholicus and even altered accumulation of bioactive compounds. It is essential to better understand the adaptive responses of metabolites in A. mongholicus to increased UV-B radiation

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