Carbon and nitrogen metabolism under nitrogen variation affects flavonoid accumulation in the leaves of Coreopsis tinctoria

Zhiyuan Li; Hong Jiang; Huizhuan Yan; Xiumei Jiang; Yan Ma; Yong Qin

doi:10.7717/peerj.12152

Carbon and nitrogen metabolism under nitrogen variation affects flavonoid accumulation in the leaves of Coreopsis tinctoria

PeerJ. 2021 Sep 10:9:e12152. doi: 10.7717/peerj.12152. eCollection 2021.

Authors

Zhiyuan Li¹, Hong Jiang¹, Huizhuan Yan¹, Xiumei Jiang¹, Yan Ma², Yong Qin¹

Affiliations

¹ College of Forestry and Horticulture, Xinjiang Agriculture University, Urumuqi, China.
² Institute of Agricultural Mechanization, Xinjiang Academy of Agricultural Sciences, Urumuqi, China.

Abstract

Flavonoids are phytochemicals present in medicinal plants and contribute to human health. Coreopsis tinctoria, a species rich in flavonoids, has long been used in traditional medicine and as a food resource. N (nitrogen) fertilization can reduce flavonoid accumulation in C. tinctoria. However, there is limited knowledge regarding N regulatory mechanisms. The aim of this study was to determine the effect of N availability on flavonoid biosynthesis in C. tinctoria and to investigate the relationship between C (carbon) and N metabolism coupled with flavonoid synthesis under controlled conditions. C. tinctoria seedlings were grown hydroponically under five different N levels (0, 0.625, 1.250, 2.500 and 5.000 mM). The related indexes of C, N and flavonoid metabolism of C. tinctoria under N variation were measured and analysed. N availability (low and moderate N levels) regulates enzyme activities related to C and N metabolism, promotes the accumulation of carbohydrates, reduces N metabolite levels, and enhances the internal C/N balance. The flavonoid content in roots and stalks remained relatively stable, while that in leaves peaked at low or intermediate N levels. Flavonoids are closely related to phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), 4-coumarate: coenzyme A ligase (4CL), and chalcone-thioase (CHS) activity, significantly positively correlated with carbohydrates and negatively correlated with N metabolites. Thus, C and N metabolism can not only control the distribution of C in amino acid and carbohydrate biosynthesis pathways but also change the distribution in flavonoid biosynthesis pathways, which also provides meaningful information for maintaining high yields while ensuring the nutritional value of crop plants.

Keywords: C. tinctoria; Carbon metabolism; Flavonoid accumulation; Nitrogen; Nitrogen metabolism.

Grants and funding

This work was supported by the National Natural Science Foundation of China (31360319), the Xinjiang Uygur Autonomous Region “13th Five-Year Plan” Horticulture Key Subject Fund Project (2016-10758-3), and the Graduate Scientific Research and Innovation Project of Xinjiang Agricultural University, China (XJAUGRI2020026). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.