Seed size is a major determinant of cereal yield, and the endosperm—the principal storage tissue in wheat—accounts for more than 80% of a mature seed's dry weight. During early development, endosperm nuclei initially divide without forming cell walls. Cellularization subsequently partitions these nuclei into individual cells and largely establishes the internal capacity of the developing grain. Auxin acts as an important developmental signal controlling this transition, while flavonoids can influence auxin transport. However, how flavonoid metabolism and auxin distribution interact to regulate endosperm cellularization and final grain size in wheat has remained poorly understood, limiting the use of this relationship in crop improvement.
A study (DOI: 10.48130/seedbio-0026-0015) published in Seed Biology on 16 June 2026 by Jirui Wang's team, Sichuan Agricultural University, reports that TaPGS1 stimulates flavonoid-pathway activity and is associated with localized auxin accumulation, moderately delayed cellularization, increased endosperm cell number, and enlarged wheat grains.
The researchers compared the wheat cultivar Fielder with two TaPGS1-overexpression lines, OE-166-6 and OE-166-39. They first measured mature-grain and field traits, finding that both engineered lines had significantly greater thousand-grain weight, grain length, and grain width. Most other agronomic characteristics and seed germination rates remained largely unchanged, suggesting that TaPGS1 overexpression predominantly affected grain size without causing major trade-offs. To investigate the underlying mechanism, the team combined liquid chromatography–mass spectrometry metabolomics with transcriptome sequencing of developing seeds. Flavonol-related metabolites showed the strongest differences between the overexpression lines and wild-type plants. Kaempferol, kaempferitrin, myricitrin, naringenin, and eriodictyol were enriched, while genes acting upstream in the flavonoid pathway and the flavonol-branch marker flavonol synthase (FLS) showed increased expression. Fluorescence staining localized the stronger kaempferol-associated signal to the inner seed coat beside the endosperm; signal intensity reached approximately twice and 1.3 times the wild-type level in OE-166-6 and OE-166-39, respectively. Immunohistochemical analysis found stronger auxin signals in the same region. Semi-thin sections of developing grains showed that wild-type seeds completed endosperm cellularization by six days post-anthesis, whereas the overexpression lines required about half a day longer. This moderate delay allowed additional nuclear divisions and was associated with an increased final number of endosperm cells. Treating wild-type seeds with 10, 25, or 50 micromolar kaempferol reproduced the cellularization delay in a concentration-dependent manner. Dual-luciferase assays further showed that TaPGS1 activated representative flavonoid-pathway promoters, including those of TaFLS, TaF3H, TaDFR, and TaCHI. Yeast two-hybrid and bimolecular fluorescence complementation assays also demonstrated that TaPGS1 interacts with TaMYB and TaWD40 proteins, consistent with its participation in a transcriptional regulatory complex.
Together, the results support a model in which TaPGS1 redirects flavonoid metabolism toward flavonol accumulation, particularly kaempferol enrichment. This change is associated with altered auxin distribution and a short delay in endosperm cellularization, creating additional endosperm cells and ultimately larger grains. Although further field evaluation and genetic validation will be needed, the study identifies a promising metabolic–hormonal pathway for improving wheat yield and potentially enhancing grain nutritional quality.
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References
DOI
10.48130/seedbio-0026-0015
Original Source URL
https://doi.org/10.48130/seedbio-0026-0015
Funding information
This research was funded by the National Key Research and Development Project (SQ2024YFF1200011), the Scientific and Technological Innovation 2030 Major Project (2023ZD04069), the National Natural Science Foundation of China (U22A20472), the Sichuan Science and Technology Support Project (2025NSFTD0025), the Technology Support Project of Chengdu (2023-YF08-00008-SN), and the open research fund of SKL-CGEUSC (SKL-ZD202212).
About Seed Biology
Seed Biology (e-ISSN 2834-5495) is published by Maximum Academic Press in partnership with Yazhou Bay Seed Laboratory. Seed Biology is an open access, online-only journal focusing on research related to all aspects of the biology of seeds, including but not limited to: evolution of seeds; developmental processes including sporogenesis and gametogenesis, pollination and fertilization; apomixis and artificial seed technologies; regulation and manipulation of seed yield; nutrition and health-related quality of the endosperm, cotyledons, and the seed coat; seed dormancy and germination; seed interactions with the biotic and abiotic environment; and roles of seeds in fruit development. Seed Biology publishes a wide range of research approaches, such as omics, genetics, biotechnology, genome editing, cellular and molecular biology, physiology, and environmental biology. Seed Biology publishes high-quality original research, reviews, perspectives, and opinions in open access mode, promoting fast submission, review, and dissemination freely to the global research community.