AUTHOR=Li Jifu , Dong Rongshu , Jia Yidan , Huang Jie , Zou Xiaoyan , An Na , Song Jianling , Chen Zhijian 

TITLE=Characterization of Metal Tolerance Proteins and Functional Analysis of GmMTP8.1 Involved in Manganese Tolerance in Soybean

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.683813

DOI=10.3389/fpls.2021.683813

ISSN=1664-462X

ABSTRACT=<p>Manganese is an essential micronutrient for plant growth but can be toxic to plants when it reaches excessive levels. Although metal tolerance proteins (MTPs), which belong to the cation diffusion facilitator (CDF) family, have been demonstrated to play critical roles in manganese (Mn) tolerance in plants, the characteristics and functions of GmMTP members in the response of soybean (<italic>Glycine max</italic>) to Mn toxicity have not been documented. In this study, growth inhibition was observed in soybean plants that were exposed to a toxic level of Mn in hydroponics, as reflected by the generation of brown spots, and decreased leaf chlorophyll concentration and plant fresh weight. Subsequent genome-wide analysis resulted in the identification of a total of 14 <italic>GmMTP</italic> genes in the soybean genome. Among these <italic>GmMTPs</italic>, 9 and 12 were found to be regulated by excess Mn in leaves and roots, respectively. Furthermore, the function of <italic>GmMTP8.1</italic>, a Mn-CDF homologue of <italic>ShMTP8</italic> identified in the legume <italic>Stylosanthes hamata</italic> that is involved in Mn detoxification, was characterized. Subcellular localization analysis showed that GmMTP8.1 was localized to the endoplasmic reticulum (ER). Heterologous expression of <italic>GmMTP8.1</italic> led to the restoration of growth of the Mn-hypersensitive yeast (<italic>Saccharomyces cerevisiae</italic>) mutant Δ<italic>pmr1</italic>, which is made defective in Mn transport into the Golgi apparatus by P-type Ca/Mn-ATPase. Furthermore, <italic>GmMTP8.1</italic> overexpression conferred tolerance to the toxic level of Mn in Arabidopsis (<italic>Arabidopsis thaliana</italic>). Under excess Mn conditions, concentrations of Mn in shoots but not roots were decreased in transgenic Arabidopsis, overexpressing <italic>GmMTP8.1</italic> compared to the wild type. The overexpression of <italic>GmMTP8.1</italic> also led to the upregulation of several transporter genes responsible for Mn efflux and sequestration in Arabidopsis, such as <italic>AtMTP8</italic>/<italic>11</italic>. Taken together, these results suggest that GmMTP8.1 is an ER-localized Mn transporter contributing to confer Mn tolerance by stimulating the export of Mn out of leaf cells and increasing the sequestration of Mn into intracellular compartments.</p>