Parthenocarpy enables cucumber ovaries to develop into fruit without pollination or fertilization, helping growers maintain yields when pollination is limited and producing seedless fruit valued by consumers. Researchers have identified numerous genetic regions associated with this trait and shown that plant hormones, including auxins, gibberellins, and brassinosteroids, influence fruit development. Applying brassinosteroids can stimulate parthenocarpic fruit set in cucumbers and several other crops. Yet the molecular link between brassinosteroid signaling and fruit formation remains unclear. Cucumber parthenocarpy is also shaped by interactions among genes and environmental conditions, making individual genetic effects difficult to isolate. Pinpointing the genes responsible for hormone responses could clarify how fruit begins to grow without fertilization and provide targets for breeding more reliable cucumber varieties.
A study (DOI: 10.48130/ph-0026-0019) published in Plant Hormones on 18 August 2026 by Ji Li's team, Nanjing Agricultural University, identifies CsBZS1 as a promising candidate underlying a fruit set region called Parth7.1 and links its elevated expression to brassinosteroid associated parthenocarpy.
To isolate the effect of Parth7.1, the team crossed a cucumber line with strong parthenocarpy, EC1, with a line that generally requires pollination to set fruit, 8419s-1. After five generations of backcrossing, they developed a near isogenic line, NIL7.1, carrying the EC1 version of the target region against a genetic background largely matching 8419s-1. They protected female flowers from pollen and assessed fruit development 10 to 12 days after flowering. NIL7.1 set fruit without pollination, while 8419s-1 did not in the genetic comparison. In a population of 457 offspring, 349 plants showed parthenocarpy and 108 did not. By comparing genetic markers with fruit set in plants carrying different segments of chromosome 7, the researchers narrowed Parth7.1 to a 111.2 kilobase region containing 16 annotated genes. They then examined sequence differences and gene expression to identify candidates. CsBZS1, which encodes a B box zinc finger protein involved in brassinosteroid signaling, stood out: it carried a 15 base pair deletion in its promoter, the region that helps control gene expression, and its expression was higher in NIL7.1. Hormone measurements also found higher levels of epibrassinolide, a brassinosteroid, in developing NIL7.1 ovaries than in 8419s-1. When the team applied epibrassinolide to 8419s-1 ovaries, fruit set without pollination increased from 12.5% in the treatment experiment’s control group to 38.4%, alongside increased CsBZS1 expression. Finally, a reporter assay comparing the two promoter versions found greater activity from the NIL7.1 version. Together, these genetic, hormone treatment and promoter results support a role for CsBZS1 in the trait, although they do not yet establish exactly how the deletion changes gene regulation.
The study connects a mapped cucumber fruit set region with a specific candidate gene and a measurable response to brassinosteroids. Its results provide a starting point for investigating how CsBZS1 controls development after flowering and for assessing its value in breeding. Further experiments are needed to establish the gene's direct effect and determine whether the promoter variant can improve fruit set across cucumber varieties and growing conditions.
###
References
DOI
10.48130/ph-0026-0019
Original Source URL
https://doi.org/10.48130/ph-0026-0019
Funding information
This work was supported by the National Natural Science Foundation of China (32272726), the Jiangsu Agricultural Science and Technology Innovation Fund (CX[24]3022), the Lhasa Key Research and Development Project (LSKJ202549), and the National Natural Science Foundation of China (62402088).
About Plant Hormones
Plant Hormones (e-ISSN 3067-221X) is an open access, online-only, academic journal publishing rigorously peer-reviewed original articles, reviews, break-through methods, editorials, and perspectives on broad aspects of plant hormone biosynthesis, signal transduction, and crosstalk. The journal primarily publishes fundamental research that represents significant advances or new insight into specialized areas of plant hormones, and review articles that provide comprehensive and critical review of current research areas and offer directions or perspectives for future research. The journal publishes applied research that has significant implications for the development of agriculture, horticulture, and forestry. Plant Hormones also provides a community forum by publishing editorials and perspective papers for expressing opinions on specific issues or new perspectives about existing research on particular topics. Plant Hormones is hosted by Chongqing University, and published by Maximum Academic Press.