Gibberellins are a family of plant hormones that have shaped agriculture for decades. They drive stem elongation, seed germination, and, crucially for growers, fruit set and expansion. But hormones are only useful to a plant when they are present in the right amount at the right place and time, which means that both their production and their destruction must be carefully controlled. That is where the GA2ox family of enzymes comes in. These enzymes, known formally as gibberellin 2-oxidases, act as molecular brakes: they convert bioactive gibberellins into inactive forms, effectively lowering the hormone signal inside plant tissues. Since the first gibberellin 2-oxidases were molecularly cloned and functionally characterised in the late 1990s, researchers have recognised C19-gibberellin 2-oxidation as a major gibberellin inactivation pathway in flowering plants, with genetic studies in Arabidopsis confirming its central role in controlling hormone levels.

What remained unclear, until now, was how one particular GA2ox gene behaves during the development of a cucurbit fruit, and whether its activity differs between the distinct tissues that make up that fruit. Cucumber fruit is an ideal system for asking this question because it can be cleanly dissected into two compartments: the pulp, the inner fleshy tissue that surrounds the developing seeds, and the pericarp, the outer fruit wall that gives the fruit its structure and its commercial appearance. These two tissues do not mature in lockstep, and previous work on gibberellin oxidase gene families in cucumber had not examined their expression with this level of tissue resolution.

The research team, led by Wenjiao Wang of the College of Horticulture at Shanxi Agricultural University, with Xiaoning An and Yupeng Liu conducting the experiments and Zhiping Liu contributing phylogenetic and promoter analyses, sampled cucumber fruit of the ‘9930’ line at five carefully chosen time points: 0, 7, 14, 21 and 28 days after pollination. This sampling strategy spans the entire arc of early fruit development, from the moment of pollination through fruit set, rapid expansion, and the beginning of maturation. At each time point, the researchers separated the pulp from the pericarp, ensuring that any differences in gene activity between the two tissues could be detected rather than averaged away, as would happen if whole fruits had been ground up for analysis.

To quantify how actively CsGA2ox2 was being transcribed in each sample, the team used quantitative real-time PCR, a technique that measures the abundance of specific messenger RNA molecules with high sensitivity. The measurements were calculated using the 2^(−ΔΔCt) method, a standard approach that normalises the target gene’s signal against a stable reference gene, in this case the Actin gene designated LOC101215469. This normalisation is essential because the total amount of RNA and the overall transcriptional activity of a tissue can vary dramatically between developmental stages, and without a reliable internal reference, comparisons across time points and tissues would be meaningless.

The results revealed a clear and consistent pattern. CsGA2ox2 was transcribed at every developmental stage the researchers examined, but its activity was not uniform. Transcript abundance was low at 0 and 7 days after pollination, the earliest phases of fruit set and initial growth. By 21 days after pollination, transcript levels had increased significantly, suggesting that the gene’s gibberellin-deactivating function ramps up as the fruit transitions through its mid-development phase. Just as striking was the tissue bias: at all stages examined, CsGA2ox2 transcripts were consistently and significantly more abundant in the pulp than in the pericarp. In other words, the inner flesh of the cucumber fruit maintains a stronger gibberellin-braking signal than the outer wall throughout development, a pattern that hints at different hormonal economies operating in the two compartments.

Beyond the expression data, the team characterised the protein that CsGA2ox2 encodes using a battery of computational, or in silico, analyses. The gene specifies a protein of 342 amino acid residues that shares between 71.84 percent and 74.96 percent amino acid identity with GA2ox homologues from other cucurbit species, placing it firmly within the evolutionary lineage of gibberellin 2-oxidases in the Cucurbitaceae family. Structural predictions painted a picture of an unstable, hydrophilic, non-secretory protein, meaning it is predicted to function inside the cell rather than being exported, and its secondary structure is dominated by random coils, flexible regions of the protein chain that lack a fixed helical or sheet-like geometry. The researchers also predicted phosphorylation sites, locations on the protein where other enzymes could attach phosphate groups to modulate its activity, a common mechanism of post-translational regulation in plant signalling proteins.

Perhaps the most intriguing computational finding came from the gene’s promoter, the stretch of DNA upstream of the coding sequence that governs when and where the gene is switched on. The team annotated the promoter’s cis-acting elements, short DNA motifs that serve as binding sites for regulatory proteins, and found elements responsive to abscisic acid, to light, and to meristem activity. Abscisic acid is another major plant hormone, often acting in opposition to gibberellins, so the presence of abscisic acid-responsive elements suggests a potential point of cross-talk between the two hormonal pathways during fruit development. Light-responsive elements hint at possible environmental modulation of the gene’s activity, while meristem-responsive elements connect the gene’s regulation to the developmental programme of actively dividing plant tissues.

The authors are careful and explicit about the limits of what their data can show. All protein-level results presented in the study are computational predictions, and they provide no direct functional evidence about what the CsGA2ox2 protein actually does inside cucumber cells. The expression data themselves are descriptive and correlative: they show that the gene’s transcript accumulation is stage- and tissue-specific, with a marked bias toward the pulp, but they do not demonstrate that this pattern causes any particular aspect of fruit development. The study is explicitly framed as a foundation for future functional studies on gibberellin catabolism in Cucurbitaceae fruit development, and the authors state that no datasets were generated or analysed beyond those reported in the study itself.

Even so, the work fills a genuine gap. Gibberellin oxidase gene families have been catalogued and characterised in a growing list of crops, including potato, apple, grape, maize, litchi, marigold, pear, and wheat, where GA2ox-related genes underpin agriculturally important traits such as dwarfism, and recent multi-omics work has implicated the gibberellin biosynthesis gene CsGA20OX1 in hormone-mediated parthenocarpy of cucumber. By adding a tissue-resolved, time-course expression profile of CsGA2ox2 to this body of knowledge, the Shanxi team has provided breeders and molecular biologists with a candidate gene whose pulp-biased, developmentally regulated expression pattern makes it a compelling target for functional studies. If future experiments confirm that CsGA2ox2 shapes gibberellin levels specifically within the developing flesh of the fruit, it could inform strategies for modulating cucumber fruit texture, size, and maturation timing, traits that matter enormously in a crop grown intensively in greenhouses around the world.

Subject of Research: Stage- and tissue-specific expression of the gibberellin 2-oxidase gene CsGA2ox2 during cucumber fruit development

Article Title: Expression profiling of the gibberellin 2-oxidase gene CsGA2ox2 (Cucumis sativus L.) reveals stage- and tissue-specific transcript accumulation during fruit development

Article References: An, X., Liu, Y., Liu, Z., & Wang, W. (2026). Expression profiling of the gibberellin 2-oxidase gene CsGA2ox2 (Cucumis sativus L.) reveals stage- and tissue-specific transcript accumulation during fruit development. Molecular Biology Reports, 53(1), Article 1679. https://doi.org/10.1007/s11033-026-12796-6

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12796-6

Keywords: cucumber, CsGA2ox2, gibberellins, GA2-oxidase, fruit development, gene expression, qRT-PCR, bioinformatics, Cucurbitaceae, plant hormones, pericarp, pulp

The study addresses a persistent blind spot in pepper science. Most previous metabolomic investigations have focused on fresh or freeze-dried fruits, leaving the biochemistry of hot air-dried peppers, the form most commonly consumed as spice powder in Korea and much of Asia, poorly characterized. Because drying concentrates and transforms metabolites, the chemical identity of a pepper powder cannot simply be inferred from fresh-fruit studies. The research team, led by scientists from Chung-Ang University and Seoul National University, harvested both cultivars at the Yeongyang Pepper Research Institute of the Rural Development Administration in August and September 2021, then dried the fruits using a standardized hot air protocol before separating the three fruit tissues for analysis.

The analytical strategy combined three complementary platforms. Gas chromatography coupled to triple quadrupole mass spectrometry quantified primary metabolites including amino acids, sugars, and fatty acids using multiple reaction monitoring. High-performance liquid chromatography with diode array detection measured carotenoids, while an integrated workflow of ultra-high-performance liquid chromatography with Orbitrap high-resolution mass spectrometry and triple quadrupole mass spectrometry annotated and quantified phenolic compounds. Capsaicinoids were determined by HPLC with ultraviolet detection. In total, the team identified 160 primary metabolites, of which 75 matched previously reported Capsicum metabolites and 85 were newly detected or structurally uncharacterized, alongside capsaicinoids, carotenoids, and 39 phenolic compounds.

Principal component analysis of the resulting data revealed a striking degree of structure. The first two components explained 89.7 percent of total variance, with the first component accounting for 58.9 percent and separating samples primarily by cultivar, and the second component accounting for 30.8 percent and separating them by tissue type. Hierarchical clustering confirmed this pattern, showing that cultivar and tissue identity, rather than harvest timing, were the dominant drivers of overall metabolic variation. This finding carries practical weight: it suggests that breeders and processors can reliably target specific cultivar-tissue combinations to obtain desired chemical profiles, while harvest date exerts a more selective influence on particular quality markers.

The amino acid results were among the most nutritionally significant. The placenta of Subicho, the landrace, contained markedly elevated levels of essential amino acids, including threonine, methionine, tryptophan, histidine, lysine, and leucine, across all tissues analyzed. The researchers interpret this as evidence of a higher capacity for protein biosynthesis in the Subicho reproductive tissue, consistent with the placenta’s role as a metabolically active organ. Subicho also accumulated substantial 4-hydroxyproline, a building block of hydroxyproline-rich glycoproteins in plant cell walls. Bulcolor, by contrast, showed higher levels of glutamic acid, the amino acid responsible for umami flavor, hinting at a sensory advantage in flavor-oriented applications.

Sugar profiles reinforced the cultivar divide. Subicho consistently contained higher concentrations of the reducing sugars glucose and fructose in placenta and pericarp tissues, roughly 1.5 to 1.7 times the levels found in Bulcolor, while Bulcolor’s pericarp held 3.7 times more sucrose than Subicho. These differences provide a physiological basis for the sensory variation between powders made from the two cultivars and could guide breeding strategies aimed at optimizing sweetness and flavor in dried pepper products.

Fatty acid and vitamin data told a story about breeding history. Bulcolor tissues accumulated higher levels of linoleic acid and alpha-linolenic acid, both essential fatty acids in the human diet and known precursors of lipid-derived plant signaling compounds. Previous work has linked fatty acid desaturase and lipoxygenase genes in Capsicum annuum to responses against tobamoviruses, and the elevated polyunsaturated fatty acid content of Bulcolor appears consistent with its development as a cultivar resistant to the resistance-breaking tomato spotted wilt virus isolate TSWV-WJ. Bulcolor was also enriched in alpha- and delta-tocopherol, antioxidants that protect against oxidative stress, and in the sterols stigmasterol and sitosterol, which contribute to membrane stability and environmental stress resistance. Subicho’s placenta, meanwhile, contained higher levels of nucleobases such as thymine, cytosine, adenine, and guanine, aligning with its amino acid abundance.

Capsaicinoid measurements delivered some of the study’s most dramatic numbers. Total capsaicinoid content ranged from 42.5 to 89.9 micrograms per gram in pericarp, 8,148.1 to 16,879.5 micrograms per gram in placenta, and just 17.3 to 85.7 micrograms per gram in seed. The placenta, which constitutes less than 4 percent of total dry weight, thus holds the overwhelming majority of a pepper’s pungency, confirming earlier estimates that it accounts for roughly 96 percent of total capsaicinoids. The single highest value, 16,879.5 micrograms per gram, was recorded in the Subicho placenta at the first harvest. In both cultivars, capsaicin concentrations fell substantially by the second harvest; Subicho placental capsaicin dropped from 9,444.7 to 5,091.8 micrograms per gram. The authors attribute this decline to metabolic changes during ripening, possibly including peroxidase-mediated degradation of capsaicinoids after maturation.

Carotenoid analysis showed a complementary tissue specialization. Six carotenoids were identified, with capsanthin, the pigment responsible for red pepper coloration and a compound associated with antioxidant and antitumor activity, consistently predominant at 155.1 to 179.9 micrograms per gram. Beta-carotene dominated the placenta at 67.3 to 97.3 micrograms per gram, while alpha-carotene appeared only in the pericarp, and no carotenoids were detected in seeds. Multivariate analysis flagged capsanthin and beta-carotene as biomarker metabolites distinguishing tissues and cultivars, and total carotenoid content was consistently higher in the pericarp than the placenta, with Bulcolor exceeding Subicho. Phenolic profiling added further resolution: chlorogenic acid was enriched in Bulcolor pericarp and placenta, vanillic acid was abundant in the Subicho placenta and in the seeds of both cultivars, and 4-hydroxybenzoic acid concentrated in seeds, where it may contribute antimicrobial and antioxidant capacity.

The practical implications extend across breeding, industry, and consumer choice. The cultivar-, tissue-, and harvest-specific database established here provides a scientific reference for selecting cultivars optimized for particular purposes, whether enhanced nutrition, pungency, color, or flavor, and for directing specific pepper tissues toward targeted uses in food processing. It also supports rigorous quality assessment of pepper powders, a product category whose commercial value depends heavily on consistent chemical composition. While the authors note that cultivar and harvest coverage in the study was limited, the framework demonstrates how comprehensive metabolomics can transform an everyday spice into a precisely engineered ingredient, giving producers evidence-based tools and consumers a clearer understanding of what determines the heat, color, and nutritional character of the red pepper on their table.

Subject of Research: Comparative metabolomic profiling of tissue-specific Korean red pepper powders from the Subicho and Bulcolor cultivars

Article Title: Comparative metabolomic profiling of tissue-specific Korean red pepper (Capsicum annuum L.) powders from Subicho and Bulcolor cultivars

Article References: Yu, H., Park, E., Lee, J.-H., Kim, S., Ku, K.-H., Choi, J. H., Chun, H. S., Lim, J.-H., & Lee, J. (2026). Comparative metabolomic profiling of tissue-specific Korean red pepper (Capsicum annuum L.) powders from Subicho and Bulcolor cultivars. Food Science and Biotechnology. https://doi.org/10.1007/s10068-026-02274-x

Image Credits: AI Generated

DOI: 10.1007/s10068-026-02274-x

Keywords: metabolomics, Capsicum annuum, Korean red pepper, capsaicinoids, carotenoids, polyphenols, Subicho, Bulcolor, placenta, pericarp, harvest timing, food science