Glycosylation is an important biochemical process that improves the solubility, stability, transport, and structural diversity of plant metabolites. This process is catalyzed by UGTs, which influence plant development, stress responses, and the production of flavonoids, including anthocyanins responsible for fruit coloration. Passion fruit is valued for its distinctive flavor and abundance of sugars, organic acids, vitamins, and health-promoting flavonoids. Although chromosome-scale genome data have enabled studies of several genes controlling its sugars, acids, aromas, and pigments, the UGT family underlying much of its metabolic diversity had not previously been systematically characterized, limiting the identification of targets for fruit-quality improvement.
A study (DOI: 10.48130/tp-0026-0009) published in Tropical Plants on 27 March 2026 by Chuanying Fang's team, Hainan University, reports 149 PeUGT genes and identifies key candidates associated with anthocyanin metabolism and ripening.
The researchers first combined protein-sequence similarity searches with hidden Markov model screening to identify proteins containing the characteristic UGT domain in the passion fruit genome. They then examined the resulting genes using phylogenetic reconstruction, chromosomal mapping, duplication analysis, gene-structure and conserved-motif comparisons, promoter-element prediction, and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses. To investigate developmental regulation, the team analyzed peel transcriptomes from fruit collected 18, 28, 41, and 58 days after flowering, representing the young-fruit, expansion, coloring, and mature stages. Each stage included three biological replicates. Co-expression network analysis and promoter-binding motif searches were subsequently integrated to predict transcription factors regulating important anthocyanin-related genes. The analysis identified 149 PeUGT genes distributed among 11 phylogenetic subfamilies. Of these, 147 were mapped unevenly across nine chromosomes, with chromosome 1 containing the largest number. Twenty tandem and 11 segmental duplication events indicated that both mechanisms contributed substantially to expansion of the family. All members contained the conserved plant secondary product glycosyltransferase box, while differences in other domains and gene structures suggested functional diversification. Promoter analysis detected 4,271 regulatory elements associated with hormone responses, growth, development, and environmental stress, including elements responsive to light, drought, low temperature, and defense signals. Functional enrichment linked the genes primarily to catalytic and secondary-metabolic processes, with ten genes associated with anthocyanin biosynthesis. Expression analysis revealed strongly stage-dependent activity: 36 genes peaked during young-fruit development, 47 during expansion, 27 during coloring, and 24 at maturity. Fourteen genes progressively increased in expression during ripening, whereas 23 declined. In particular, PeUGT10 and PeUGT17 peaked at the expansion stage before decreasing, while PeUGT38 increased throughout development and reached its highest level at maturity. Regulatory-network analysis predicted 28, two, and 20 candidate transcription factors for these three genes, respectively, with G2-like transcription factors shared across all three networks.
Overall, the study establishes a genomic and regulatory framework for understanding UGT-mediated glycosylation in passion fruit. The results connect gene-family evolution with developmental expression and identify PeUGT10, PeUGT17, and PeUGT38 as priority candidates for investigating pigment production and stability. Because the proposed regulatory relationships are based largely on computational and transcriptomic evidence, experimental validation will be needed to confirm gene functions and transcription-factor interactions. Nevertheless, the resource can support marker-assisted selection and genome-editing strategies for developing passion fruit varieties with enhanced coloration, nutritional value, and environmental adaptability.
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References
DOI
10.48130/tp-0026-0009
Original Source URL
https://doi.org/10.48130/tp-0026-0009
Funding information
This research was supported by the Key R & D Project of Baoting Li and Miao Autonomous County (Grant No. BTZDYF2025001) and the Project of Sanya Yazhou Bay Science and Technology City (Grant No. SKJC-JYRC-2024-29).
About Tropical Plants
Tropical Plants (e-ISSN 2833-9851) is the official journal of Hainan University and published by Maximum Academic Press. Tropical Plants undergoes rigorous peer review and is published in open-access format to enable swift dissemination of research findings, facilitate exchange of academic knowledge and encourage academic discourse on innovative technologies and issues emerging in tropical plant research.