Apple vacuolar sugar transporters regulated by MdDREB2A enhance drought resistance by promoting accumulation of soluble sugars and activating ABA signaling

Abstract

Soluble sugars are not only an important contributor to fruit quality, but also serve as the osmotic regulators in response to abiotic stresses. Early drought stress promotes sugar accumulation, while specific sugar transporters govern the cellular distribution of the sugars. Here, we show that apple plantlets accumulate soluble sugars in leaf tissues under drought stress. Transcriptional profiling of stressed and control plantlets revealed differential expression of several plasma membrane—or vacuolar membrane-localized sugar transporter genes. Among these, four previously identified vacuolar sugar transporter (VST) genes (MdERDL6-1, MdERDL6-2, MdTST1, and MdTST2 ) showed higher expression under drought, suggesting their roles in response to drought stress. Promoter cis -elements analyses, yeast one-hybrid, and dual-luciferase tests confirmed that the drought-induced transcription factor MdDREB2A could promote the expression of MdERDL6-1/ − 2 and MdTST1/2 by binding to their promoter regions. Moreover, overexpressing of each of these four MdVSTs alone in transgenic apple or Arabidopsis plants accumulated more soluble sugars and abscisic acid (ABA), and enhanced drought resistance. Furthermore, apple plants overexpressing MdERDL6-1 also showed reduced water potential, facilitated stomatal closure, and reactive oxygen species scavenging under drought conditions compared to control plants. Overall, our results suggest a potential strategy to enhance drought resistance and sugar accumulation in fruits through manipulating the genes involved in vacuolar sugar transport.

Acknowledgements

This work was supported by the Young Elite Scientists Sponsorship Program by CAST (2023QNRC001), the National Key Research and Development Program of China (2023YFD2301000), the China Postdoctoral Science Foundation (2023 T160536, 2023 M742870), the Shaanxi Association for Science and Technology Young Talents Lifting Project (20230201), and the Shaanxi Postdoctoral Research Funding Project (2023BSHTBZZ24). We are grateful to Dr Jing Zhang, Dr Yangyang Yuan, and Dr Ruihong Chen (SU5000, Hitachi, Japan) from the Horticulture Science Research Center, Northwest A&F University, Yangling, China, for providing professional technical assistance. We thank Prof. Steven van Nocker (Michigan State University) for scientific suggestions and writing modifications in the revision stage.

Author contributions

M.L., F.M., Y.R., and L.Z. designed the experiments. L.Z., C.Z., N.Y., W.C., Y.L., Y.P., X.W., and B.M. performed the experiments and analyzed the data. L.Z. drafted the manuscript. M.L., F.M., and Y.R. revised the manuscript. All authors provided final approval of this manuscript.

Data Availability

The data underlying this article are available in the article and in its online supplementary material.

Conflict of interest statement

The authors declare no competing interests.

Supplementary data

Supplementary data is available at Horticulture Research Journal online.

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