Search Results (4)

MADS-box transcription factors have undergone in-depth investigations regarding their function in regulating the development of plant floral organs. Flower type mutants serve as critical biological models for investigating the regulatory mechanisms of MADS-box genes in floral organ development, while simultaneously constituting essential genetic resources for molecular breeding programs. In this work, we examined a lip-like sepal of the peloric mutant in Phalaenopsis ‘Huayang’, which exhibited changes in both the morphology and color of the sepals. Our cryo-SEM investigations revealed that the mutation type belonged to a sepal labellum-like variation in Phalaenopsis ‘Huayang’. Nine glycosylated anthocyanins were identified and their contents were significantly upregulated in the Se-red of mutant flowers. Transcriptomic analysis identified 9408 differentially expressed genes, including 4934 upregulated and 4474 downregulated genes. In addition, 57 MADS-box genes were identified and classed into five groups (Mα, Mβ, Mγ, MIKC*, and MIKC^C) according to a phylogenetic comparison with Arabidopsis homologs. Furthermore, 29 MADS genes were screened from the MIKC^C group, and these genes may play a crucial role in the regulation of floral organ development. Through real-time PCR analysis and protein interaction analysis, we identified three genes that were upregulated in the mutant, which may be involved in sepal development. The subcellular localization results demonstrated that three genes were found within the nucleus. Taken together, our results elucidated the molecular mechanism of sepal variation in Phalaenopsis ‘Huayang’. Our results could enhance our comprehension of the regulatory mechanisms underlying floral patterning and promote the molecular breeding process of Phalaenopsis. Full article

Orchids have evolved flowers with unique morphologies through coevolution with pollinators, such as insects. Among the floral organs, the lip (labellum), one of the three petals, exhibits a distinctive shape and plays a crucial role in attracting pollinators and facilitating pollination in many orchids. The lip of the terrestrial orchid Habenaria radiata is shaped like a flying white bird and is believed to attract and provide a platform for nectar-feeding pollinators, such as hawk moths. To elucidate the mechanism of lip morphogenesis, we conducted time-lapse imaging of blooming flowers to observe the extension process of the lip and analyzed the cellular morphology during the generation of serrations. We found that the wing part of the lip folds inward in the bud and fully expands in two hours after blooming. The serrations of the lip were initially formed through cell division and later deepened through polar cell elongation. Transcriptome analysis of floral buds revealed the expression of genes involved in floral organ development, cell division, and meiosis. Additionally, genes involved in serration formation are also expressed in floral buds. This study provides insights into the mechanism underlying the formation of the unique lip morphology in Habenaria radiata. Full article

Orchid flowers have a unique structure that consists of three sepals and three petals, with one of the petals forming the labellum (lip) that can be differentiated into the hypochile and epichile. In orchids, the emission of floral scent is specific and spatially complex. Little is understood about the molecular and biochemical mechanisms of the differing scent emissions between the parts of orchid flowers. Here, we investigated this in the Cattleya hybrid KOVA, and our study showed that monoterpenes, including linalool and geraniol, are the main components responsible for the KOVA floral scent. The KOVA flower was scentless to the human nose before it reached full bloom, potentially because the 1-deoxy-d-xylulose 5-phosphate synthases (RcDXSs) and 4-hydroxy-3-methylbut-2-enyl diphosphate synthases (RcHDSs) that biosynthesize monoterpenes were highly expressed in flowers only when it reached full flowering. Additionally, the spatial expression profile of the monoterpene synthases (RcMTPSs), which were highly expressed in the basal region of the lip (hypochile), contributed to the highest monoterpene emissions from this part of the flower. This might have caused the hypochile to be more fragrant than the other parts of the flower. These findings enrich our understanding of the difference in scents between different flower parts in plants and provide information to breed novel orchid cultivars with special floral scents. Full article

Floral organs have evolved from leaves for reproduction, and the morphological analyses help to understand the plant diversity and evolution. Habenaria radiata (syn. Pecteilis radiata) is a terrestrial orchid living in wetlands in Japan, Russia, South Korea, and China. The habitats of this plant in Japan have been reduced because of environmental destruction and overexploitation, and thus it is on the Red List of Japan as a Near Threatened species. One of the three petals of the H. radiata flower is called a lip or labellum, which resembles a flying white bird, egret, or white heron, with its proposed function being to attract pollinators. To understand the diversity of H. radiata plants in different areas, we examined the lip morphology and phylogeny of populations from eight habitats in the Kinki area, Japan. The complex shapes of the lips were quantified and presented as a radar chart, enabling characterization of the morphological difference among populations. Phylogenetic analysis with microsatellite markers that we generated showed the variation of genetic diversity among populations, suggesting the different degrees of inbreeding, outbreeding, and vegetative propagation. Our approach offers a basic method to characterize the morphological and genetic diversity in natural populations. Full article