Amino acid pathway discovery offers new route to salt-resilient tomatoes
image: A proposed model for the role of SlAAP6 in the salt stress response.
Credit: Horticulture Research
Tomatoes, one of the world's most important horticultural crops, often struggle to grow in saline soils that limit yields and quality. A new study identifies the amino acid permease gene SlAAP6 as a critical transporter that increases branched-chain amino acid (BCAA) accumulation, enhances biomass production, and improves salt tolerance in tomato plants. By promoting root elongation and reducing oxidative stress through better amino acid distribution, SlAAP6 overexpression significantly strengthened tomato development compared with wild types or mutants. This work demonstrates how manipulating amino acid transport can simultaneously improve crop nutrition, growth, and environmental resilience, paving the way for genetic improvement strategies to ensure stable tomato production under challenging soil conditions.
Tomato plants are rich in diverse metabolites, including amino acids, which are fundamental for protein synthesis, plant growth, and stress responses. Branched-chain amino acids (BCAAs)—leucine, isoleucine, and valine—play particularly important roles in regulating root growth, cell division, and responses to salinity. Although biosynthetic pathways for these amino acids have been partly described, much less is known about their uptake and transport within tomato tissues. Previous evidence from rice and Arabidopsis suggests amino acid transporters are central to growth and stress resilience. Based on these challenges, there is a need to investigate the specific roles of BCAA transporters in tomato growth and salt tolerance.
Researchers from Hainan University and collaborators published (DOI: 10.1093/hr/uhae286) their findings on October 11, 2024, in Horticulture Research. The article details how SlAAP6 functions as a transporter that enhances BCAA uptake and distribution across plant tissues. The study demonstrates that SlAAP6 overexpression increases amino acid content, biomass accumulation, and root elongation, while also conferring improved tolerance to saline conditions compared to wild-type or knockout tomato plants.
The team began with a metabolic genome-wide association study (mGWAS) of 374 tomato accessions, which identified SlAAP6 as strongly linked to BCAA content. Functional assays confirmed its transporter role: expression in yeast and frog oocytes restored amino acid uptake, particularly for leucine and isoleucine. In tomato plants, SlAAP6 was highly expressed in roots, pollen, and vascular tissues. Overexpression lines (SlAAP6-OE) accumulated higher levels of free amino acids and nitrogen, resulting in greater shoot and root biomass, while knockout mutants (slaap6) showed reduced amino acid levels and stunted growth. Under salt stress, SlAAP6-OE seedlings maintained longer roots and lower reactive oxygen species (ROS) accumulation, supported by enhanced peroxidase and glutathione-related enzyme activity. Supplementation with exogenous BCAAs, especially leucine, further improved root growth and antioxidant capacity. The study concludes that SlAAP6 promotes amino acid absorption, redistribution, and stress resilience by coordinating nitrogen metabolism and ROS detoxification. This dual role highlights SlAAP6 as both a growth promoter and a stress defender, making it a promising candidate for tomato genetic improvement.
“Our results provide direct evidence that amino acid transporters, particularly SlAAP6, are not only central to tomato growth but also to stress tolerance,” said corresponding author Prof. Jun Yang. “By linking nitrogen assimilation, root development, and ROS detoxification, SlAAP6 demonstrates how a single transporter can control multiple physiological processes. This discovery offers a new strategy for breeding tomatoes that are more resilient to salinity while improving nutritional quality, addressing both food security and climate-related agricultural challenges.”
The identification of SlAAP6 as a regulator of BCAA transport provides a new genetic target for crop engineering. By enhancing amino acid uptake and redistribution, breeders can create tomato varieties that perform better in saline soils, which affect large agricultural regions worldwide. Beyond tomatoes, insights into amino acid transporter function may be transferable to other crops, offering a general strategy for boosting growth, nitrogen use efficiency, and resilience against abiotic stress. Integrating SlAAP6 into breeding programs could therefore help stabilize yields, improve fruit quality, and ensure food production sustainability under increasingly adverse environmental conditions.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhae286
Funding information
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).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.