Cucumber (Cucumis sativus L.) is a major vegetable crop worldwide, and its yield and quality are closely linked to flower development. AGAMOUS-LIKE 6 (AGL6), a member of the ancient MADS-box transcription factor family, plays a crucial role in flower development. However, the specific functions of its homolog in cucumber remain poorly understood. In this study, we demonstrate that CsAGL6 is predominantly expressed in flowers, with high expression levels observed in all floral organ primordia during the early stages of floral development. The petals of Csagl6 mutants exhibit a greener color compared to wild-type plants, along with a significant increase in total chlorophyll content. Additionally, the mutants show abnormal petal morphology, including changes in size and shape, as well as enlarged sepals resembling leaves occasionally. Molecular analysis reveals that CAULIFLOWER (CAL) and the E-class gene SEPALLATA 4 (SEP4) are significantly downregulated in the mutants, while the chlorophyll synthesis gene Early Light-Induced Protein 1 (ELIP1) and several stress-related genes in the chloroplasts are dramatically upregulated. Our findings provide novel insights into the functional role of CsAGL6 in regulating sepal and petal development, and offer a potential avenue for understanding the genetic control of flower pigmentation and organ morphology in Cucumis species.

Melon (Cucumis melo L.) is an important horticultural crop, with fruit formation and yield closely linked to the proper development of floral organs. Understanding floral organogenesis in melon is therefore essential for enhancing agricultural productivity. In this study, we identified a mutant with abnormal floral morphology from an EMS-mutagenized melon population. Genetic analysis revealed that this phenotype is controlled by a single recessive gene. Utilizing MutMap+ and linkage analysis, we pinpointed the candidate gene responsible for this trait as the UNUSUAL FLORAL ORGANS (UFO) gene in melon. A single nucleotide polymorphism (C to T) was found to cause a nonsynonymous mutation in a conserved site of the CmUFO protein. Moreover, CRISPR/Cas9-generated CmUFO mutants exhibited phenotypic characteristics consistent with those of EMS-induced mutants. Transcriptomic analysis indicated that a set of genes associated with flower development were down-regulated in the mutant, suggesting that CmUFO plays a conserved role in floral organ development in melon. This study provides valuable insights into the mechanisms underlying floral organogenesis in melon.