Peach fruit quality depends not only on yield and appearance but also on aroma, which is largely determined by volatile esters and lactones produced during ripening. In modern orchards, nitrogen fertilizers are frequently applied in excess to maximize productivity. However, high nitrogen inputs have long been associated with poorer flavor, including reduced sweetness and weakened aroma intensity. Although enzymes and transcription factors involved in volatile biosynthesis have been identified, the molecular mechanisms linking nitrogen nutrition to aroma regulation have remained largely unresolved. In particular, how nitrogen signaling interferes with transcriptional networks controlling key aroma compounds has been unclear, creating a major knowledge gap at the intersection of fertilization practices and fruit sensory quality.
Researchers from Shandong Agricultural University report new insights into how nitrogen fertilization controls peach aroma at the molecular level. Published (DOI: 10.1093/hr/uhaf256) in Horticulture Research in 2025, the study demonstrates that excessive nitrogen suppresses γ-decalactone accumulation by activating a protein-kinase-centered regulatory module. Through field experiments, gene expression profiling, and functional validation in peach fruit and plant systems, the team reveals how nitrogen signaling rewires transcriptional regulation and protein activity to reduce aroma biosynthesis, directly linking fertilization practices to fruit sensory quality.
Using multi-year nitrogen treatments in peach orchards, the researchers first showed that high nitrogen application sharply reduces γ-decalactone levels, in some cases below detectable limits. Gas chromatography–mass spectrometry confirmed that nitrogen suppresses multiple aroma-related lactones and esters, while transcript analysis revealed coordinated downregulation of biosynthetic genes such as PpAAT2, PpAAT3, PpLOX1, PpLOX6, and PpFAD3.
The study then identified two NAC transcription factors, PpNAC6 and PpNAC36, whose expression strongly correlates with γ-decalactone production. Functional assays demonstrated that both factors directly bind to the promoters of aroma-biosynthetic genes and activate their transcription. Silencing either gene reduced γ-decalactone accumulation, whereas overexpression enhanced aroma-related gene expression.
Crucially, the work uncovered a nitrogen-responsive kinase, PpSnRK1α, as the upstream regulator. Under high nitrogen conditions, PpSnRK1α interacts with PpNAC6 and PpNAC36 and selectively phosphorylates PpNAC36, weakening its transcriptional activity. This phosphorylation, together with nitrogen-induced relocalization of NAC proteins from the nucleus to the cytoplasm, suppresses aroma biosynthesis. Together, these results define a nitrogen-controlled molecular switch that directly connects fertilization to fruit aroma quality.
“Our findings explain, at the molecular level, why excessive nitrogen fertilization often leads to peaches with weaker aroma,” said one of the study’s senior authors. “By identifying the PpSnRK1α–PpNAC6/PpNAC36 module, we show how nitrogen signaling actively represses key aroma genes rather than affecting flavor indirectly. This mechanism highlights that fruit quality is not simply a by-product of growth, but the outcome of tightly regulated signaling networks that respond to nutrient inputs.”
The discovery has direct implications for both orchard management and crop improvement. By clarifying how nitrogen suppresses aroma biosynthesis, the study provides a scientific basis for optimizing fertilizer strategies that balance yield with sensory quality. Beyond management practices, the identified regulatory module offers molecular targets for breeding or biotechnological approaches aimed at maintaining strong aroma under variable nitrogen conditions. More broadly, the work illustrates how nutrient signaling can reshape fruit quality traits, supporting precision fertilization and sustainable horticulture practices that prioritize flavor alongside productivity.
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References
DOI
10.1093/hr/uhaf256
Original Source URL
https://doi.org/10.1093/hr/uhaf256
Funding information
This work is supported by China Agricultural Research System (No. CARS-30-2-02), the grants from the Agricultural Improved Variety Engineering Program of Shandong Province (2024LZGCQY021), project ZR2024MC193 supported by Shandong Provincial Natural Science Foundation and project ZR2022QC019 supported by Shandong Provincial Natural Science Foundation.
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.