A proposed model of VlMYB59-VlCKX4 regulatory module function during CPPU-induced grape fruit set. Left, under normal development conditions, grapes undergo physiological berry abscission resulting in a low fruit set rate. Without CPPU treatment, the VlMYB59-VlCKX4 module-mediated pathway for regulating the fruit set is not activated. Right, CPPU treatment induces the VlMYB59 gene expression. The binding of the VlMYB59 transcription factor to the cis-acting element TAACCA on the VlCKX4 promoter positively regulates the VlCKX4 expression. Gene VlCKX4 acts as a positive regulatory factor to promote fruit set. Arrows represent a positive regulatory action of one component on another.
News — Fruit set in grapes plays a decisive role in yield and quality but is often challenged by significant berry abscission during early development. While plant hormones like cytokinins have been applied to mitigate these issues, their effects were not fully understood at the molecular level. This gap in knowledge spurred a deeper investigation into cytokinin-induced genetic pathways.
Led by researchers from the College of Horticulture and Plant Protection at Henan University of Science and Technology, and in on July 10, 2024, the study explores how N-(2-chloro-4-pyridyl)-N′-phenylurea (CPPU) influences the fruit set process. Using dynamic transcriptomic analysis of ‘Kyoho’ grape berries treated with CPPU, the researchers identified the VlMYB59 transcription factor and VlCKX4 gene as critical regulators. Together, they form a regulatory module within the cytokinin metabolic pathway, enhancing fruit retention and development.
The research uncovered a complex interaction between the VlMYB59 transcription factor and VlCKX4 gene. VlMYB59 binds to VlCKX4's promoter, activating a pathway that regulates cytokinin metabolism and promotes fruit set. Validation in Arabidopsis confirmed that overexpressing these genes significantly enhanced fruit retention and overall plant growth. Additionally, the study introduced an innovative approach to identifying valuable differentially expressed genes (VDEGs), refining the precision of key regulatory gene mapping. These findings reveal how CPPU treatment reshapes cytokinin homeostasis to mitigate berry abscission, offering critical insights into the genetic control of fruit development. The study not only advances the understanding of cytokinin regulation but also provides genetic tools for breeding high-yield grape varieties, marking a milestone in horticultural science.
Dr. Yihe Yu, lead author, highlighted the significance of the discovery: "This work represents a major step forward in decoding how cytokinins govern fruit set. The VlMYB59-VlCKX4 module provides a promising target for breeding efforts aimed at enhancing grape productivity and quality."
This study has the potential to change grape farming for the better. By focusing on the VlMYB59-VlCKX4 module, scientists can develop grape varieties that keep more young berries and produce higher yields. The research also explains how CPPU, a plant growth regulator, works to control key hormones, paving the way for smarter, more efficient use of such treatments. These breakthroughs not only solve major challenges in grape growing but also support eco-friendly and cost-effective farming methods, making grape production both more sustainable and profitable.
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This work was supported by National Natural Science Foundation of China (Grant No. 32072517), Program for Science & Technology Innovation Talents in Universities of Henan Province (Grant No. 21HASTIT035), Top Young Talents in Central Plains (Grant No. Yuzutong (2021)44), and PhD Research Startup Foundation of Henan University of Science and Technology (Grant No. 13480077).
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