New genetic pathway unlocks seedless pear production
image: Expression levels of PbCYP78A6 and PbMYB56 linked to GA4+7-induced pseudo-embryo development and parthenocarpy.
Credit: Horticulture Research
Seedless fruit production, known as parthenocarpy, offers major commercial advantages by improving eating quality, reducing labor costs, and stabilizing yields under poor pollination conditions. However, the regulatory mechanisms driving parthenocarpy remain poorly understood in woody fruit crops. This study identifies a regulatory module involving PbDELLA, PbMYB56, and PbCYP78A6 that governs gibberellin (GA)-induced pseudo-embryo development and parthenocarpic fruit set in pears. The transcription factor PbMYB56 directly activates PbCYP78A6 to promote cell proliferation, while PbDELLA, a key component of GA signaling, suppresses this activation. Manipulating this regulatory pathway alters fruit initiation, seed development, and fruit size. The findings enhance our understanding of hormone-mediated fruit set and provide genetic targets for breeding seedless pear varieties.
Parthenocarpy naturally occurs when fruits develop without fertilization, and has been widely applied in crops such as tomato, citrus, grape, and pear to satisfy consumer preference for seedlessness. In pears, successful fruit set is strongly restricted by self-incompatibility and pollination constraints, which often lead to yield instability. Gibberellins (GA), particularly GA4+7, are known to induce parthenocarpic fruit development, yet the downstream transcriptional signaling mechanisms remain unclear. Recent studies have suggested that cytochrome P450 family genes contribute to cell proliferation and ovule integument expansion, processes central to parthenocarpy. Due to these challenges, deeper investigation is needed to clarify how GA signaling triggers seedless fruit formation in pears.
Researchers from Northwest A&F University (China) conducted a study published (DOI: 10.1093/hr/uhaf021) on May 1, 2025, in Horticulture Research, revealing molecular insights into GA4+7-induced parthenocarpy in Pyrus bretschneideri. The team identified a regulatory module involving PbDELLA, PbMYB56, and PbCYP78A6 that promotes pseudo-embryo development and fruit initiation in the absence of fertilization. Functional verification using pear and tomato transgenic systems confirmed the module’s role in regulating cell proliferation and seed development.
The researchers first observed that GA4+7 treatment induced the formation of a “pseudo-embryo” in unpollinated pear ovaries, closely resembling seed tissues produced through normal fertilization. Transcriptome analysis revealed that PbCYP78A6, a cytochrome P450 gene previously linked to cell proliferation, was strongly upregulated during this process. A yeast one-hybrid screen identified PbMYB56 as a direct transcriptional activator of PbCYP78A6, and electrophoretic mobility shift assays confirmed the binding of PbMYB56 to MYB-binding motifs on the PbCYP78A6 promoter.
Genetic overexpression of PbMYB56 in pear and tomato enhanced fruit retention, increased cell layer thickness in the ovary wall, and enabled parthenocarpic fruit development following emasculation. Conversely, silencing of SlMYB56 in tomato reduced fruit size and seed development, but these defects were rescued by PbCYP78A6 overexpression. Further protein interaction assays demonstrated that PbDELLA, a GA-signaling repressor, physically interacts with PbMYB56, reducing its transcriptional activation of PbCYP78A6. Co-overexpression of PbDELLA with PbMYB56 abolished parthenocarpy and decreased fruit and seed size. Collectively, these results identify PbDELLA–PbMYB56–PbCYP78A6 as a core signaling module linking GA signaling to pseudo-embryo formation and parthenocarpic fruit set.
“Our findings reveal a previously unknown regulatory mechanism that connects GA perception to pseudo-embryo development and seedless fruit production,” said the study's corresponding author. “The PbDELLA–PbMYB56–PbCYP78A6 module functions as a molecular switch that determines whether a fruit develops with or without fertilization. Understanding this regulatory logic opens opportunities to breed stable, high-quality seedless pear cultivars without relying heavily on exogenous hormone treatments.”
This discovery provides new genetic targets for breeding seedless pear varieties, which can increase fruit market value and decrease production losses caused by poor weather or pollinator shortages. By manipulating PbMYB56 or PbCYP78A6 expression, breeders may induce stable parthenocarpy without the need for repeated hormone applications. Additionally, because this pathway is functionally conserved in tomato, the findings may extend to other fruit crops where seedlessness is desirable. Future research will focus on optimizing gene-editing strategies to develop commercial cultivars with enhanced fruit quality and yield stability.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhaf021
Funding information
This research was funded by the China Agriculture Research System (CARS 28) and the Weinan Experimental Station Foundation of Northwest A&F University (2023WNXNZX-4).
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.