Research has identified a single transcription factor, CsNPF1, that regulates both parthenocarpic fruit formation and bitterness in cucumbers. This discovery stems from the genetic mapping of a natural non-parthenocarpic mutant, named npf1, found in the cucumber inbred line 10Y.
The npf1 mutant exhibits a loss of parthenocarpy, which is the ability of a plant to produce fruit without fertilization. The study revealed that while wild-type 10Y fruits grow significantly in size without pollination, npf1 fruits cease to develop, leading to fruit abortion. Anatomical analysis indicated that ovule development was halted in npf1, preventing normal fruit formation.
To pinpoint the genetic locus associated with the npf1 phenotype, researchers conducted bulked-segregant analysis and identified a 5-Mb region on chromosome 6. Further analysis narrowed this down to a 378.6-kb region containing 50 protein-coding genes. Among these, CsNPF1 was found to be specifically expressed in the shoot apex and ovary of the wild-type plants but not in the npf1 mutant.
CsNPF1 encodes a transcription factor belonging to the APETALA2/Ethylene Responsive Factor (AP2/ERF) family, which plays a crucial role in regulating gene expression involved in fruit development. The study also demonstrated that a deletion in the CsNPF1 gene in the npf1 mutant is responsible for its non-parthenocarpic phenotype.
Moreover, the research explored the implications of CsNPF1 on fruit quality, revealing that npf1 fruits are significantly more bitter than those of the wild-type. This bitterness is linked to higher levels of cucurbitacin C, a compound responsible for the bitter taste in cucumbers. The findings suggest that CsNPF1 not only influences fruit development but also impacts the sensory qualities of the fruit.
Overall, the identification of CsNPF1 provides a potential target for future cucumber breeding programs aimed at improving fruit quality and yield.