How grape berries adapt their carbon metabolism to cope with limited sugar supply
image: Weighted gene coexpression network analysis of DEGs and five berry traits (berry FW, glucose concentration, fructose concentration, and hexose concentration) of fruit-cutting berries in Experiment 2, and KEGG enrichment of DEGs in ‘turquoise’ module. (a) Module–trait relationship and P-values (in parentheses). Color in right panel shows correlation from −1 to 1. In left panel, 12 modules are represented by different colors. (b) Module–treatment relationship and correlation coefficient. The left panel indicates different samples. 69 DC1, 69D, 69 days after treatment; C, control; 1, first repetition. 69DCL1, 69D, 69 days after treatment; CL, carbon limitation; 1, first repetition. (c) Functional enrichment analysis with KEGG pathway annotation in ‘turquoise’ module. Image link: https://academic.oup.com/view-large/figure/507806100/uhae363f6.tif?login=false
Credit: Horticulture Research
Rising temperatures and irregular rainfall driven by global climate change are causing grapes to accumulate excess sugars and lose acidity, threatening the delicate balance crucial for winemaking. Grape sugar concentration depends on the source-to-sink ratio—the balance between photosynthetic leaf area and fruit load—which determines the flow of carbon from leaves to berries. Previous studies have explored sugar and acid changes, but the combined regulation of metabolites, enzymes, and transcripts during carbon limitation remains unclear. Understanding how grape berries reorganize their metabolic network under limited carbon supply is vital to develop climate-resilient viticulture. Due to these challenges, in-depth investigations into grape carbon metabolism are urgently needed.
A research team from the Institute of Botany, Chinese Academy of Sciences, in collaboration with INRAE and the University of Bordeaux, published (DOI: 10.1093/hr/uhae363) their findings on April 1, 2025, in Horticulture Research. Using Vitis vinifera cv. Cabernet Sauvignon as a model, they manipulated carbon supply by leaf removal to study how berries respond to a low source-to-sink ratio. Through integrated metabolomic, enzymatic, and transcriptomic analyses, the study uncovered the intricate metabolic adjustments that help grape berries sustain homeostasis under carbon limitation.
The researchers analyzed grapes grown with reduced leaf area (two or three leaves per cluster) and measured dynamic changes in metabolites, enzyme activities, and gene expression across berry development. Under carbon limitation, sucrose, glucose, and fructose levels dropped by about 27–30%, yet glycolytic intermediates—such as glucose-6-phosphate, 3-phosphoglycerate, and phosphoenolpyruvate—increased, suggesting a metabolic rerouting to sustain energy production. Amino acids like glutamine, arginine, and serine accumulated significantly, while proline and γ-aminobutyric acid declined, indicating altered nitrogen flux and osmotic regulation. Transcriptomic data revealed thousands of differentially expressed genes enriched in carbohydrate and amino acid metabolism pathways, forming coordinated networks that preserve internal balance. Surprisingly, most enzymes showed little change in maximal activity, implying that post-translational or flux-level controls, rather than enzyme abundance, governed these metabolic adjustments. Correlation analyses further showed reduced connectivity between metabolites and enzyme activities under carbon limitation, reflecting the plasticity of grape metabolism in adapting to stress.
“Grape berries operate like finely tuned metabolic systems,” said Prof. Zhanwu Dai, corresponding author of the study. “Even when carbon input is reduced, the berries maintain internal equilibrium by reshaping the relationships among metabolites, enzymes, and genes. This flexibility enables them to survive and develop in challenging environments. Our results suggest that carbon limitation does not simply slow metabolism—it reprograms it to sustain essential functions.”
This integrative analysis reveals how grape berries balance carbon and nitrogen metabolism under stress, providing valuable clues for vineyard management and breeding. By adjusting the source-to-sink ratio, viticulturists may control sugar accumulation and prevent overly alcoholic wines as climates warm. Moreover, the study’s multi-omics framework offers a roadmap for exploring metabolic resilience in other fruit crops. Future research integrating proteomics and metabolic flux analysis could identify key regulatory nodes, helping develop cultivars optimized for sustainable production under environmental constraints.
###
References
DOI
10.1093/hr/uhae363
Original Source URl
https://doi.org/10.1093/hr/uhae363
Funding information
This research was supported partly by National Natural Science Foundation of China (grant 32072519), the National Key R&D Program of China (2021YFE0109500), National Natural Science Foundation of China (U20A2041), the Frimouss (ANR-15-CE20-0009), Agricultural Breeding Project of Ningxia Hui Autonomous Region (NXNYYZ202101), CAS Youth Interdisciplinary Team (JCTD-2022-06), and CAS Project for Young Scientists in Basic Research (YSBR-093).
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, 2024. 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.