Flower opening and final petal size are determined largely by the extent of cell expansion rather than cell division. In roses, petal growth depends on tightly controlled remodeling of the cell wall, especially the synthesis of cellulose, which provides structural support during expansion. Gibberellins are known to stimulate cell enlargement in many plant organs, yet how these hormones interact with transcriptional regulators and cell wall biosynthesis pathways has remained unclear. Previous studies suggested that hormone signaling, transcription factors such as MYB family members, and cellulose synthases all play roles in petal development, but their integration into a unified regulatory framework was missing. Based on these challenges, it was necessary to conduct an in-depth investigation into the molecular coordination of hormone signaling and cell wall regulation in rose petals.
Researchers from the Yunnan Academy of Agricultural Sciences and China Agricultural University reported (DOI: 10.1093/hr/uhaf134) on May 21, 2025, in Horticulture Research, a detailed molecular mechanism controlling petal size in roses. By combining hormone treatments, gene silencing, transcriptome analysis, and biochemical assays, the team demonstrated that gibberellins regulate petal expansion through a feedback loop involving the transcription factor RhMYB70. This mechanism links hormone biosynthesis via RhGA3ox3 with cellulose production mediated by RhCESA8, revealing how rose petals achieve precise size control during flower opening.
The study first showed that endogenous gibberellin levels increase sharply during early stages of rose flower opening, coinciding with rapid petal cell expansion. External application of gibberellin significantly enlarged petals by increasing individual cell size rather than cell number. Transcriptome analysis identified RhMYB70, an R2R3-MYB transcription factor, as a key negative regulator suppressed by gibberellin treatment. Silencing RhMYB70 resulted in larger petals and expanded epidermal cells, confirming its inhibitory role in growth.
Further experiments revealed that RhMYB70 directly binds to the promoter of RhCESA8, a cellulose synthase gene, repressing its expression. Reduced RhMYB70 activity led to increased cellulose accumulation in petals, strengthening the cell wall while allowing greater expansion. In parallel, RhMYB70 was shown to repress RhGA3ox3, a gene involved in gibberellin biosynthesis. When RhMYB70 levels declined, gibberellin production increased, creating a feedback loop that sustained growth-promoting signals. This dual regulation positions RhMYB70 as a central node linking hormone metabolism and cell wall construction.
According to the researchers, this feedback mechanism explains how plants balance flexibility and strength during organ growth. By integrating hormonal signaling with transcriptional control of cellulose synthesis through RhCESA8 and hormone biosynthesis via RhGA3ox3, the system allows petals to expand rapidly while maintaining mechanical integrity. The authors emphasize that such finely tuned regulation is essential for ornamental plants, where even subtle changes in organ size can have major economic impacts. They note that transcriptional regulators like RhMYB70 may serve as key leverage points for precise trait modulation.
The findings provide clear molecular targets for improving flower quality in ornamental breeding. Manipulating components of the gibberellin–RhMYB70–cellulose pathway could allow precise control over petal size without compromising structural stability or developmental timing. Beyond roses, the study offers insights relevant to other crops where organ size influences yield, aesthetics, or market value. Understanding how hormone feedback loops coordinate with cell wall biosynthesis genes such as CESA family members may also inform strategies to optimize plant growth under variable environmental conditions.
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References
DOI
10.1093/hr/uhaf134
Original Source URL
https://doi.org/10.1093/hr/uhaf134
Funding information
This work was supported by the National Natural Science Foundation of China (Grant number 32202530), Talent Introduction and Training Project of Yunnan Academy of Agricultural Sciences (Grant number 2024RCYP-09), Yunnan Province Agricultural Joint Key Project (Grant number 202401BD070001-016), and Fundamental Research Project (Grant number 202401CF070046), and Xingdian Talent Support Program (Grant number XDYC-QNRC-2023-0457).
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.