The amino acid permease SlAAP6 contributes to tomato growth and salt tolerance by mediating branched-chain amino acid transport

Abstract

Branched-chain amino acids (BCAAs) are essential amino acids in tomato (Solanum lycopersicum) required for protein synthesis, which also modulate growth and abiotic stress responses. To date, little is known about their uptake and transport in tomato especially under abiotic stress. Here, the tomato amino acid permease 6 (SlAAP6) gene was identified as an amino acid transporter that restored mutant yeast cell growth on media with a variety of amino acids, including BCAAs. Overexpression of SlAAP6 (SlAAP6-OE) in tomato raised the BCAA content and elevated the fresh weight, while SlAAP6 knockouts (slaap6) showed reduced levels of neutral and basic amino acids in seedling tissues and lower total free amino acid distribution to shoots. In comparison to wild type and slaap6 mutants, SlAAP6-OE alleviated root limited growth by elevated BCAA transport and upregulated the expression of root-growth-related genes by increasing BCAAs in vivo. As SlAAP6 serves as a positive regulator for BCAA abundance, SlAAP6-OE lines showed greater salinity tolerance, while slaap6 mutants exhibited increased salt sensitivity. The salt tolerance of SlAAP6-OE plants was further enhanced by the application of exogenous BCAAs. In addition, BCAA supplementation reduced the accumulation of H₂O₂ in root under salt stress conditions. Based on these findings, SlAAP6-mediated uptake and transport of BCAAs facilitated growth and salt tolerance in tomato. By characterizing this key amino acid transporter, this study provides a novel approach to simultaneously enhance tomato nutritional quality, growth and development, and stress resistance through genetic improvement.

Acknowledgements

We thank Chuanyou Li (Institute of Genetics and Developmental Biology, Chinese Academy of Sciences) for providing us with the pK7WGF2 and pTX41 vectors and Guillaume Pilot (Virginia Polytechnic Institute and State University, USA) for providing us with yeast strains 22Δ10α and 23344c and Jo ̈rg Kudla (Universita ̈tMu ̈nster, Germany) for ER marker RFP-HDEL and plasma membrane marker CBL1n-OFP. This work was supported by the Hainan Provincial Natural Science Foundation of China (323CXTD373), the National Key R&D Program of China (No. 2022YFF1001900), the National Natural Science Foundation of China (No. 32100212), the Hainan Province Science and Technology Special Fund (No. ZDYF2022XDNY144), the Hainan Provincial Academician Innovation Platform Project (No. HD-YSZX-202004), the Young Elite Scientists Sponsorship Program by CAST (No. 2019QNRC001), and the Hainan University Startup Fund (No. KYQD (ZR) 21025).

Author contributions

S.W. and Jun Yang conceived the project and supervised the study. Q.Q., Z.Z., X.L., and X.D. performed the experiments. Q.Q., C.L., and X.L. collected and analyzed the data. Q.Q., Z.Z., M.M., J.Z., S.L., Z.L., W.Y., P.C., and Jie Yang participated in material preparations. Q.Q., Z.Z., S.W., and Jun Yang wrote the original draft. All authors discussed the results and commented on the manuscript.

Data availability

All data generated during the study are provided in this article and the supplementary files.

Conflict of interest statement

The authors declare that they have no competing interests.

Supplementary Data

Supplementary data is available at Horticulture Research online.

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