SlbHLH36-<i>SlAAP8</i> alleviates heat-induced pollen abortion by regulating amino acid metabolism in tomato

Xiangyu Ding; Qi Qiang; Guo Xu; Wenyu Zhao; Zhonghui Zhang; Chao Wang; Xumin Ou; Jie Yang; Shouchuang Wang; Jun Yang

doi:10.1016/j.jgg.2026.03.002

Turn off MathJax

Article Contents

Article Navigation > Journal of Genetics and Genomics > 2026 > Accepted Manuscript

PDF( 0 KB)

SlbHLH36-SlAAP8 alleviates heat-induced pollen abortion by regulating amino acid metabolism in tomato

doi: 10.1016/j.jgg.2026.03.002

a. State Key Laboratory of Tropical Crop Breeding, School of Breeding and Multiplication (Sanya Institute of Breeding and Multiplication), Hainan University, Sanya, Hainan 572025, China;
b. State Key Laboratory of Tropical Crop Breeding, College of Tropical Agriculture and Forestry, Hainan University, Sanya, Hainan 572025, China

Funds:

D Program of China (2021YFA0909600), the National Natural Science Foundation of China (32460072, 32502732), the Hainan Provincial Natural Science Foundation of China (323CXTD373), the Hainan Provincial Academician Innovation Platform Project (HD-YSZX-202004), and the Collaborative Innovation Center of Nan-fan and High-Efficiency Tropical Agriculture (XTCX2022NYB06).

We sincerely thank Professor Chuanyou Li (Shandong Agricultural University) for supplying the pBI121 and pTX041 vectors. Additionally, we acknowledge Professor Guillaume Pilot (Virginia Polytechnic Institute and State University) for providing the yeast strains 22Δ10α and 23344c, as well as Professor Jörg Kudla (University of Münster) for supplying the endoplasmic reticulum marker protein OFP::HDEL, the plasma membrane marker protein OFP::CBL and the nuclear marker protein PIF4::mCherry. This study was supported by the National Key R&

Received Date: 2025-10-09
Accepted Date: 2026-03-03
Rev Recd Date: 2026-03-03

Available Online: 2026-03-11

Abstract

Abstract

Under environmental stress, plants dynamically reprogram amino acid metabolism and long-distance transport to facilitate efficient nutrient reallocation. However, amino acid transporters in tomato remain poorly characterized, especially with respect to their functional roles, transcriptional regulation, and influence on pollen fertility under heat stress. In this study, a metabolite-based genome-wide association study (mGWAS) identifies an amino acid transporter, amino acid permease 8 (SlAAP8), that is significantly associated with the content of multiple amino acids. SlAAP8 is primarily expressed in tomato flowers and exhibits broad-spectrum amino acid transport activity. Overexpression of SlAAP8 (SlAAP8-OE) promotes amino acid accumulation in stamen tissues and enhances pollen viability under high-temperature conditions. Furthermore, we identify a transcription factor, SlbHLH36, that directly binds to the E-box (CANNTG) motif in the SlAAP8 promoter and activates its transcription. Heat stress significantly upregulates the expression of both SlbHLH36 and SlAAP8, thereby improving pollen viability under high-temperature conditions by modulating amino acid metabolism and antioxidant activity, as well as reducing malondialdehyde (MDA) accumulation. Together, these findings suggest that the SlbHLH36-SlAAP8 module enhances tomato pollen viability under heat stress through regulating amino acid metabolism and scavenging reactive oxygen species (ROS), providing a potential avenue to improve crop yields under global warming.
- Amino acid permease,
- Heat stress,
- Pollen viability,
- Transcriptional regulation,
- Tomato

FullText(HTML)

References(56)

References

Batistic, O., Waadt, R., Steinhorst, L., Held, K., Kudla, J., 2010. CBL-mediated targeting of CIPKs facilitates the decoding of calcium signals emanating from distinct cellular stores. Plant J. 61, 211-222.

Begcy, K., Nosenko, T., Zhou, L.Z., Fragner, L., Weckwerth, W., Dresselhaus, T., 2019. Male sterility in maize after transient heat stress during the tetrad stage of pollen development. Plant Physiol. 181, 683-700.

Besnard, J., Pratelli, R., Zhao, C., Sonawala, U., Collakova, E., Pilot, G., Okumoto, S., 2016. UMAMIT14 is an amino acid exporter involved in phloem unloading in Arabidopsis roots. J. Exp. Bot. 67, 6385-6397.

Cao, P., Yang, J., Xia, L., Zhang, Z., Wu, Z., Hao, Y., Liu, P., Wang, C., Li, C., Yang, J., et al., 2024. Two gene clusters and their positive regulator SlMYB13 that have undergone domestication-associated negative selection control phenolamide accumulation and drought tolerance in tomato. Mol. Plant 17, 579-597.

Chaturvedi, P., Wiese, A.J., Ghatak, A., Zaveska, Drabkova. L., Weckwerth, W., Honys, D., 2021. Heat stress response mechanisms in pollen development. New Phytol. 231, 571-585.

Chen, J., Wu, J., Lu, Y., Cao, Y., Zeng, H., Zhang, Z., Wang, L., Wang, S., 2016. Molecular cloning and characterization of a gene encoding the proline transporter protein in common bean (Phaseolus vulgaris L.). Crop J. 4, 384-390.

Cosco, J., Regina, T.M.R., Scalise, M., Galluccio, M., Indiveri, C., 2019. Regulatory aspects of the vacuolar CAT2 arginine transporter of S. lycopersicum: role of osmotic pressure and cations. Int. J. Mol. Sci. 20, 906.

Dai, W., Wang, M., Gong, X., Liu, J. H., 2018. The transcription factor FcWRKY40 of Fortunella crassifolia functions positively in salt tolerance through modulation of ion homeostasis and proline biosynthesis by directly regulating SOS2 and P5CS1 homologs. New Phytol. 219, 972-989.

Deng, L., Wang, H., Sun, C., Li, Q., Jiang, H., Du, M., Li, C.B., Li, C., 2018. Efficient generation of pink-fruited tomatoes using CRISPR/Cas9 system. J. Genet. Genomics 45, 51-54.

Dinkeloo, K., Boyd, S., Pilot, G., 2018. Update on amino acid transporter functions and on possible amino acid sensing mechanisms in plants. Semin. Cell Dev. Biol. 74, 105-113.

Dobritzsch, S., Weyhe, M., Schubert, R., Dindas, J., Hause, G., Kopka, J., Hause, B., 2015. Dissection of jasmonate functions in tomato stamen development by transcriptome and metabolome analyses. BMC Biol. 13, 28.

Fang, Z., Wu, B., Ji, Y., 2021. The amino acid transporter OsAAP4 contributes to rice tillering and grain yield by regulating neutral amino acid allocation through two splicing variants. Rice (New York, NY) 14, 2.

Galili, G., Amir, R., Fernie, A.R., 2016. The regulation of essential amino acid synthesis and accumulation in plants. Annu. Rev. Plant Biol. 67, 153-178.

Ghosh, U.K., Islam, M.N., Siddiqui, M.N., Cao, X., Khan, M.A.R., 2022. Proline, a multifaceted signalling molecule in plant responses to abiotic stress: understanding the physiological mechanisms. Plant Biol. 24, 227-239.

Giorno, F., Wolters-Arts, M., Grillo, S., Scharf, K.D., Vriezen, W.H., Mariani, C., 2010. Developmental and heat stress-regulated expression of HsfA2 and small heat shock proteins in tomato anthers. J. Exp. Bot. 61, 453-462.

Guo, H., Li, C., Lai, J., Tong, H., Cao, Z., Wang, C., Zhao, W., He, L., Wang, S., Yang, J., et al., 2023. Comprehensive analysis of metabolome and transcriptome reveals the regulatory network of coconut nutrients. Metabolites 13, 683.

Guo, M., Zhang, X., Liu, J., Hou, L., Liu, H., Zhao, X., 2020. OsProDH negatively regulates thermotolerance in rice by modulating proline metabolism and reactive oxygen species scavenging. Rice (New York, NY) 13, 61.

Guo, N., Hu, J., Yan, M., Qu, H., Luo, L., Tegeder, M., Xu, G., 2020. Oryza sativa Lysine-Histidine-type transporter 1 functions in root uptake and root-to-shoot allocation of amino acids in rice. Plant J. 103, 395-411.

Guo, N., Xue, D., Zhang, W., Zhao, J.M., Xue, C.C., Yan, Q., Xue, J.Y., Wang, H.T., Zhang, Y.M., Xing, H., 2016. Overexpression of GmProT1 and GmProT2 increases tolerance to drought and salt stresses in transgenic Arabidopsis. J. Integr. Agric. 15, 1727-1743.

Hao, Y., Wang, X., Guo, L., Xiang, L., Luo, E., Cao, P., Liu, P., Zhong, Y., Li, C., Lai, J., et al., 2025. JA-mediated regulation of amino acid homeostasis adjusts metabolic flux and enhances spider mite tolerance via the SlJAZ8-SlWRKY57-SlAVT6s module in tomato. Adv. Sci. 12, e16717.

Hao, Y., Xiang, L., Lai, J., Li, C., Zhong, Y., Ye, W., Yang, J., Yang, J., Wang, S., 2023. SlERF.H6 mediates the orchestration of ethylene and gibberellin signaling that suppresses bitter-SGA biosynthesis in tomato. New Phytol. 239, 1353-1367.

He, M., Wu, J., Yang, Y., Cui, Q., Fan, N., Chi, C., Yan, H., Liu, Y., Pan, Z., Zhang, K., et al., 2025. The HsfA1a-BAG5b module mediates thermotolerance through activating autophagy in tomato. Plant Physiol. 199, kiaf526.

Heinemann, B., Hildebrandt, T.M., 2021. The role of amino acid metabolism in signaling and metabolic adaptation to stress-induced energy deficiency in plants. J. Exp. Bot. 72, 4634-4645.

Hijaz, F., Killiny, N., 2019. Exogenous GABA is quickly metabolized to succinic acid and fed into the plant TCA cycle. Plant Signal. Behav. 14, e1573096.

Hirner, A., Ladwig, F., Stransky, H., Okumoto, S., Keinath, M., Harms, A., Frommer, W.B., Koch, W., 2006. Arabidopsis LHT1 is a high-affinity transporter for cellular amino acid uptake in both root epidermis and leaf mesophyll. Plant Cell 18, 1931-1946.

Hosseinifard, M., Stefaniak, S., Ghorbani, Javid, M., Soltani, E., Wojtyla, L., Garnczarska, M., 2022. Contribution of exogenous proline to abiotic stresses tolerance in plants: a review. Int. J. Mol. Sci. 23, 5186.

Huang, W., Ma, D., Zaman, F., Hao, X., Xia, L., Zhang, E., Wang, P., Wang, M., Guo, F., Wang, Y., et al., 2024. Identification of the lysine and histidine transporter family in Camellia sinensis and the characterizations in nitrogen utilization. Hortic. Plant J. 10, 273-287.

Jiang, Z., van Zanten, M., Sasidharan, R., 2025. Mechanisms of plant acclimation to multiple abiotic stresses. Commun. Biol. 8, 655.

Lee, Y.H., Foster, J., Chen, J., Voll, L.M., Weber, A.P., Tegeder, M., 2007. AAP1 transports uncharged amino acids into roots of Arabidopsis. Plant J. 50, 305-319.

Li, F., Dong, C., Yang, T., Bao, S., Fang, W., Lucas, W.J., Zhang, Z., 2021. The tea plant CsLHT1 and CsLHT6 transporters take up amino acids, as a nitrogen source, from the soil of organic tea plantations. Hortic. Res. 8, 178.

Li, H.L., Xiang, L.T., Zhao, X.D., Zhu, B.Z., Zhu, H.L., Qu, G.Q., Luo, Y.B., Gao, Y., Jiang, C.Z., Fu, D.Q., 2025. Functional redundancy of transcription factors SlNOR and SlNOR-like1 is required for pollen development in tomato. Hortic. Res. 12, uhaf003.

Liu, X., Bush, D.R., 2006. Expression and transcriptional regulation of amino acid transporters in plants. Amino Acids 30, 113-120.

Okumoto, S., Koch, W., Tegeder, M., Fischer, W.N., Biehl, A., Leister, D., Stierhof, Y.D., Frommer, W.B., 2004. Root phloem-specific expression of the plasma membrane amino acid proton co-transporter AAP3. J. Exp. Bot. 55, 2155-2168.

Omari, A.F., 2021. Genome wide analysis of amino acid transporter superfamily in Solanum lycopersicum. Plants 10, 289.

Ouonkap, S.V.Y., Palaniappan, M., Pryze, K., Jong, E., Foteh, Ali M., Styler, B., Althiab, Almasaud. R., Harkey, A.F., Reid, R.W., Loraine, A.E., et al., 2024. Enhanced pollen tube performance at high temperature contributes to thermotolerant fruit and seed production in tomato. Curr. Biol. 34, 5319-5333.

Qian, D., Li, T., Zheng, C., Wang, M., Chen, S., Li, C., An, J., Yang, Y., Niu, Y., An, L., et al., 2025. Heat-stable protein PGSL1 enhances pollen germination and tube growth at high temperature. Nat. Commun. 16, 3642.

Qiang, Q., Zhang, Z., Li, X., Li, C., Mao, M., Ding, X., Zhang, J., Li, S., Lai, Z., Yang, J., et al., 2024. The amino acid permease SlAAP6 contributes to tomato growth and salt tolerance by mediating branched-chain amino acid transport. Hortic. Res. 12, uhae286.

Santiago, J.P., Tegeder, M., 2016. Connecting source with sink: the role of Arabidopsis AAP8 in phloem loading of amino acids. Plant Physiol. 171, 508-521.

Schwacke, R., Grallath, S., Breitkreuz, K.E., Stransky, E., Stransky, H., Frommer, W.B., Rentsch, D., 1999. LeProT1, a transporter for proline, glycine betaine, and gamma-amino butyric acid in tomato pollen. Plant Cell 11, 377-392.

Shi, Y., Zhang, Y., Sun, Y., Xie, Z., Luo, Y., Long, Q., Feng, J., Liu, X., Wang, B., He, D., et al., 2023. Natural variations of OsAUX5, a target gene of OsWRKY78, control the neutral essential amino acid content in rice grains. Mol. Plant 16, 322-336.

Sun, Y., Shi, Y., Liu, G., Yao, F., Zhang, Y., Yang, C., Guo, H., Liu, X., Jin, C., Luo, J., 2020. Natural variation in the OsbZIP18 promoter contributes to branched-chain amino acid levels in rice. New Phytol. 228, 1548-1558.

Tao, J., Kong, W., Luo, W., Wang, L., Dai, X., Lin, X., Dong, H., Yang, X., Mo, B., Chen, X., et al., 2024. The rice microRNA159-SPOROCYTELESS EAR2 module regulates starch biosynthesis during pollen development and maintains male fertility. Plant Cell 37, koae324.

Taylor, M.R., Reinders, A., Ward, J.M., 2015. Transport function of rice amino acid permeases (AAPs). Plant Cell Physiol. 56, 1355-1363.

The, S.V., Santiago, J.P., Pappenberger, C., Hammes, U.Z., Tegeder, M., 2024. UMAMIT44 is a key player in glutamate export from Arabidopsis chloroplasts. Plant Cell 36, 1119-1139.

Verbruggen, N., Hua, X.J., May, M., Van, Montagu. M., 1996. Environmental and developmental signals modulate proline homeostasis: evidence for a negative transcriptional regulator. Proc. Natl. Acad. Sci. U. S. A. 93, 8787-8791.

Wang, T., Li, Y., Huang, Y., Zhao, X., Dong, Z., Jin, W., Huang, W., 2022. Amino acid permease 6 regulates grain protein content in maize. Crop J. 10, 1536-1544.

Wang, X., Rossi, M.L., Martinelli, A.P., Angenent, G.C., de Maagd, R.A., 2025. FRUITFULL2 controls tomato fertility through style length and pollen quality. Hortic. Plant J. 11, 1896-1904.

Wang, Y., Xie, D., Zheng, X., Guo, M., Qi, Z., Yang, P., Yu, J., Zhou, J., 2024. MAPK20-mediated ATG6 phosphorylation is critical for pollen development in Solanum lycopersicum L. Hortic. Res. 11, uhae069.

Wu, M., Zhang, Q., Wu, G., Zhang, L., Xu, X., Hu, X., Gong, Z., Chen, Y., Li, Z., Li, H., et al., 2023. SlMYB72 affects pollen development by regulating autophagy in tomato. Hortic. Res. 10, uhac286.

Yao, X., Nie, J., Bai, R., Sui, X., 2020. Amino acid transporters in plants: identification and function. Plants (Basel) 9, 972.

Zdunek-Zastocka, E., Grabowska, A., Branicki, T., Michniewska, B., 2017. Biochemical characterization of the triticale TsPAP1, a new type of plant prolyl aminopeptidase, and its impact on proline content and flowering time in transgenic Arabidopsis plants. Plant Physiol. Biochem. 116, 18-26.

Zhang, L., Chen, X., Wu, Y., 2023. Research progress on proline in plant stress resistance. Journal of Jianghan University (Natural Science Edition), 51, 42-51.

Zhao, C., Pratelli, R., Yu, S., Shelley, B., Collakova, E., Pilot, G., 2021. Detailed characterization of the UMAMIT proteins provides insight into their evolution, amino acid transport properties, and role in the plant. J. Exp. Bot. 72, 6400-6417.

Zhu, G., Wang, S., Huang, Z., Zhang, S., Liao, Q., Zhang, C., Lin, T., Qin, M., Peng, M., Yang, C., et al., 2018. Rewiring of the fruit metabolome in tomato breeding. Cell 172, 249-261.

Zhu, H., Han, G., Wang, J., Xu, J., Hong, Y., Huang, L., Zheng, S., Yang, J., Chen, W., 2023. CG hypermethylation of the bHLH39 promoter regulates its expression and Fe deficiency responses in tomato roots. Hortic. Res. 10, uhad104.

Zhu, J.Y., Sun, Y., Wang, Z.Y., 2012. Genome-wide identification of transcription factor-binding sites in plants using chromatin immunoprecipitation followed by microarray (ChIP-chip) or sequencing (ChIP-seq). Methods Mol. Biol. 876, 173-188.

Relative Articles

Supplements(0)

Cited By

Proportional views