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The rice bean ( Vigna umbellata) root apex specifically secretes citrate through expression activation of Vigna umbellata Multidrug and Toxic Compound Extrusion 1 ( Vu MATE1) under aluminum (Al3+) stress. However, the underlying mechanisms regulating Vu MATE1 expression remain unknown., We isolated and characterized a gene encoding Sensitive to Proton Rhizotoxicity1 ( STOP1)-like protein, Vu STOP1, from rice bean. The role of Vu STOP1 in regulating Vu MATE1 expression was investigated using the yeast one-hybrid assay. We characterized the function of Vu STOP1 in Al3 + - and H+-tolerance using in planta complementation assays., We demonstrated that Vu STOP1 has transactivation potential. We found that Vu STOP1 expression is inducible by Al3+ and H+ stress. However, although Vu STOP1 binds to the promoter of Vu MATE1, the inconsistent tissue localization patterns of Vu STOP1 and Vu MATE1 preclude Vu STOP1 as the major factor regulating Vu MATE1 expression. In addition, when a protein translation inhibitor increased expression of Vu STOP1, Vu MATE1 expression was inhibited. In planta complementation assay demonstrated that Vu STOP1 could fully restore expression of genes involved in H+ tolerance, but could only partially restore expression of At MATE., We conclude that Vu STOP1 plays a major role in H+ tolerance, but only a minor role in Al3+ tolerance. The differential transcriptional regulation of Vu STOP1 and Vu MATE1 reveals a complex regulatory system controlling Vu MATE1 expression. [ABSTRACT FROM AUTHOR]

Nitrogen (N) remobilization from mature leaves to new shoots (NSs) is closely related to the quality of green tea in the spring season, which subsequently determines its economic value. However, the underlying N remobilization mechanism remains poorly understood. Here, we demonstrate that >80% of the recovered 15N was partitioned in the first mature leaves that supply NSs. N-remobilization efficiency (NRE) from mature leaves to NSs varied significantly among tea cultivars. N-fertilization level and NRE showed a significantly positive correlation. Based on weighted gene co-expression network analysis, glutamate metabolism-related genes, including glutamine synthetase genes, CsGSs, were dissected from the interaction network of hub genes regulating N remobilization. Gene expression patterns and the localization of CsGS1.1 in the cytosol and vascular tissue suggest its potential role in N remobilization. Consistent with these findings, source-to-sink N remobilization at the reproductive stage was enhanced in transgenic CsGS1.1-overexpressing plants. Furthermore, we demonstrated that the Dof transcription factor CsDof16 directly binds to the -526 to -426 region of the CsGS1.1 promoter, thereby activating its transcription and regulating N remobilization. Taken together, our findings suggest that the CsDof16-CsGS1.1 module regulates the remobilization of N in the form of glutamate/glutamine from mature leaves to NSs, constituting an important control point in the regulation of source-to-sink N partitioning in tea plants. Our findings can be employed to reduce fertilizer application and promote the development of sustainable tea production., Competing Interests: Conflict of interest statement. None declared., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society of Plant Biologists. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

To provide guidance for the safe use of organic fertilizers and improve soil quality and tea safety, it is necessary to conduct systematic analyses of the heavy metal content of organic fertilizers applied in the main tea producing areas of China. In this study, we analyzed the heavy metal contents in organic fertilizer samples collected from 2017 to 2019. The risks of collected organic fertilizers from different areas and sources were calculated. The results showed that the average concentrations of ω (As), ω (Hg), ω (Pb), ω (Cd), ω (Cr), ω (Cu), ω (Zn), and ω (Ni) in the collected organic fertilizers were 4.60, 0.22, 27.1, 0.78, 27.9, 58.3, 250.1, and 16.3 mg·kg -1 , respectively. According to the assessment standard in NY/T 525- 2021, the over-limit rates of As, Hg, Pb, Cd, and Cr were 6.19%, 1.33%, 4.42%, 4.42%, and 1.33%, respectively. With respect to the area, the qualified rates were 100% in Shaanxi, Jiangsu, Anhui, Fujian, and Guangxi; 80%-90% in Shandong, Zhejiang, Hubei, Sichuan, Yunnan, and Guangdong; and only 54.5% in Jiangxi. The qualified rates of sources were 100% in rapeseed cake, soybean cake, and pig manure; 95.8% in sheep manure; 91.7% in cow manure; 90.7% in chicken manure; 87.2% in manure of other animals; 82.4% in the mixture of plant and animal sources; 65.2% in other plant sources; and 63.6% in other sources. According to the recommended application rate, the accumulation rate of heavy metals in soil with pig manure, cow manure, chicken manure, and sheep manure would be much higher than that with rapeseed cake and soybean cake. The average accumulation rate of organic fertilizer from animal sources was 7-30 times higher than that from plant sources. Therefore, it is recommended to use rapeseed cake or soybean cake fertilizer in tea plantation and to increase the supervision of heavy metal accumulation in soil and tea in those high-risk areas.