Drought stress is a major environmental challenge that threatens crop productivity worldwide, especially in fruit trees like apples. When plants face water shortages, they often accumulate osmoprotectants like soluble sugars to maintain cell function and reduce oxidative damage. Sugar transporters located on cell and vacuolar membranes mediate this process, determining how sugars are distributed and stored. While vacuolar sugar transporters (VSTs) have been linked to fruit sweetness, their role in stress adaptation remains underexplored. Moreover, the transcription factor DREB2A is known to regulate drought-responsive genes, but its downstream targets in sugar metabolism are still being uncovered. Due to these challenges, it is essential to investigate the genetic mechanisms underlying sugar transport and drought resilience in apples.
Researchers from Northwest A&F University published a study (DOI: 10.1093/hr/uhae251) on September 3, 2024, in Horticulture Research, uncovering a novel mechanism that connects sugar metabolism and drought resistance in apple plants. The team identified four key vacuolar sugar transporter genes regulated by the transcription factor MdDREB2A, and demonstrated that overexpressing these genes enhances sugar accumulation, reduces water loss, and promotes abscisic acid (ABA) signaling during drought. This work provides valuable genetic targets for breeding apple varieties that are both sweeter and more resilient to climate stress.
Using transcriptomic analysis, the researchers identified that MdERDL6–1, MdERDL6–2, MdTST1, and MdTST2 were significantly upregulated in apple leaves under drought stress. Yeast one-hybrid and dual-luciferase assays confirmed that MdDREB2A directly activates these genes by binding to DRE elements in their promoters. Transgenic apple and Arabidopsis plants overexpressing any of the four VST genes accumulated more soluble sugars—particularly glucose, fructose, and sucrose—under drought conditions. These sugar increases contributed to reduced leaf water potential and slower water loss.
Further analysis showed that overexpression of MdERDL6–1 not only preserved photosynthetic activity but also enhanced reactive oxygen species (ROS) scavenging by boosting antioxidant enzyme levels. Additionally, these transgenic plants exhibited stronger ABA signaling, with elevated expression of ABA biosynthesis genes (MdNCED1/3) and downstream response genes like MdSnRK2.6 and MdAREB1.1/1.2/1.3. Importantly, stomatal apertures were smaller in the transgenic lines, supporting improved water retention. The integration of sugar transport and hormone signaling provides a comprehensive defense strategy against drought, making these genes attractive targets for apple breeding.
“This research breaks new ground in linking sugar transport and hormone signaling to drought resistance,” said Professor Mingjun Li, corresponding author of the study. “By manipulating MdDREB2A and its downstream VST genes, we can enhance sugar accumulation and improve water-use efficiency in apple plants. These genes not only make apples sweeter but also help the trees survive under increasingly frequent droughts. It’s a win-win for both growers and consumers.”
This study provides a dual-purpose strategy for apple improvement—enhancing both drought tolerance and fruit sweetness by regulating vacuolar sugar transport. Such genetic insights are especially valuable in the context of climate change, where water scarcity threatens fruit production. The MdDREB2A–VST regulatory module offers breeders a clear molecular target to develop new apple cultivars that thrive in dry environments while producing high-quality fruit. Beyond apples, this approach may be transferable to other horticultural crops, offering a broader blueprint for improving stress resilience and nutritional value simultaneously.
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References
DOI
10.1093/hr/uhae251
Original Source URL
https://doi.org/10.1093/hr/uhae251
Funding information
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.
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.