Mechanisms involved in the positive effects of high zinc on growth of Sedum alfredii

Abstract

Abstract Background and Aims: Zinc (Zn) is an essential micronutrient for plant growth, and excessive Zn in the soil can inhibit normal plant growth, adversely affecting plant health. Sedum alfredii Hance, a native Zn/Cd hyperaccumulator plant species in China, has strong tolerance and ability to accumulate heavy metals. Previous studies have reported that Zn may have a positive effect on S. alfredii growth, rather than causing toxicity. Thus, exploring the growth-promoting mechanisms of high Zn concentrations on S. alfredii may provide a theoretical reference for phytoremediation technologies. Methods: In this study, the hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) of S. alfredii as research subjects, we used metabolomics, metabolomics, and transcriptomics techniques to explore. Results: At 250 μM Zn, HE root biomass and Zn concentration in roots increased, while being reduced in NHE. Nano-XRF analysis showed that Zn was located in the cortical intercellular space in HE roots, whereas Zn was scattered in the root cells in NHE. The content of auxin in HE roots was increased by 1.26 times and the auxin oxidase activity decreased by 2.94 times after exposure to 100 μM Zn for 12 h, while NHE exhibited the opposite trend. Transcriptomic results showed that HE up-regulated genes were related to carbohydrate metabolism, nitrogen metabolism, carbon fixation, and tryptophan biosynthesis; down-regulated genes were related to lipid metabolism and linoleic acid metabolism. Conclusion: We further screened key gene resources, laying a foundation for the molecular mechanism underlying the positive effect of high Zn concentration on HE growth.