Abstract
Malate transporters play pivotal roles in plant aluminum tolerance mechanisms. In the classic aluminum tolerance pathway, Al3+ induces ALMT, which promotes malate exudation to chelate Al3+ to enhance aluminum tolerance. However, in tomato, SlALMT was inhibited by Al3+, but Al3+ still induced malate exudation. We found that SlSLAH2, upon induction by Al3+, can transport malate and is required for full activation of malate exudation by Al3+ stress. SlWRKY37 contributes to SlSLAH2 induction by Al3+. Moreover, SlSLAH2 is phosphorylated in response to Al3+. We identify SlCDPK21 and SlPP2C72 as putative upstream kinase and phosphatase that could potentially facilitate phosphorylation homeostasis. SlCDPK21 can interact with SlSLAH2 in a heterologous system, phosphorylate SlSLAH2 at Thr167 in vitro and is also required for full malate exudation. SlPP2C72 can dephosphorylate SlSLAH2 in vitro and knock-out leads to increased malate exudation. Furthermore, Al3+ downregulated SlPP2C72, and Al3+ treated seedling extracts can suppress SlPP2C72 phosphatase activity. We propose a synergistic transcription-phosphorylation cascade that can ensure a robust malate exudation across Al3+ environments.
Data availability
The authors declare that the data supporting the findings of this study are available within the paper and its supplementary information files. Source data are provided with this paper.
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Acknowledgements
We thank Professor Jianmin Wan (State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, Nanjing Agricultural University) for providing Escherichia coli wild type strain K12 (CGSC4401), Escherichia coli dicarboxylate transport mutant strain CBT315 (CGSC5269) and pKK223-3 vector. We thank Professor Yi Wang (State Key Laboratory of Plant Environmental Resilience, College of Biological Sciences, China Agricultural University) for providing pGEMHE vector. This work was supported by the grants from National Natural Science Foundation of China (32172599 to Y-DG), the Open Research Fund of State Key Laboratory of Efficient Utilization of Agricultural Water Resources (SKLAWR-2025Y-03 to NZ), Beijing Rural Revitalization Agricultural Science and Technology Project (NY2401080000 to Y-DG), Beijing Agriculture Innovation Consortium (BAIC01-2026 to Y-DG) and the 2115 Talent Development Program of China Agricultural University (to Y-DG and NZ).
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Y.-D.G., N.Z., and D.D. designed this project and wrote the manuscript. D.D. performed most of the experiments. D.D., C.J., and J.Z. analyzed the data. W.Y., G.M., J.G., S.C., W.Z., and Z.L. participated in this work. TL and JY provided valuable assistance during revision. All authors read and approved the final manuscript.
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Dong, D., Jia, C., Zhang, J. et al. SlSLAH2 mediates malate exudation and contributes to aluminum tolerance. Nat Commun (2026). https://doi.org/10.1038/s41467-026-71651-1
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DOI: https://doi.org/10.1038/s41467-026-71651-1
