Homeotic Orchid Tepal (HOT) Model for Explicating Floral Morphogenesis in Orchidaceae

  • 潘 昭君

Student thesis: Doctoral Thesis


The typical orchid floral morphology architecturally consists of three sepals two petals together with the most sophisticated lip and colum Previous studies reveal that lip plays a critical role in orchid pollination strategies Orchid flower remarkable for its zygomorphic syndrome is intently related to the Orchidaceae evolutionary history The evolution of lip is one of the major factors for orchid flower exhibiting zygomorphy to derived from the actinomorphy lily-like flower This thesis investigates the B- and E-class MADS genes in determining orchid floral organ identities and the Homeotic Orchid Tepal (HOT) model is proposed for explicating floral morphogenesis in Orchidaceae Tweenty seven AP3-like and 14 PI-like genes from 12 species of orchids were widely identified Homologous genes of PI clade and four duplicated AP3A1 AP3A2 AP3B1 and AP3B2 subclades were conserved in the orchid family Among the four AP3 subclades the lip specificity of orchid AP3A2 orthologs was demonstrated by the differential transcript between petal and lip of normal flowers and by the ectopic expression in lip-like petal of orchids with peloric flowers Although an AP3A2-like gene was identified in lily-like Neuwiedia flower without obviously modified lip the primitive AP3A2 maybe necessary but not sufficient for regulating lip development Based on these results the HOT model was proposed in which dualistic characters of duplicated B-class MADS-box genes are involved in orchid perianth development and growth especially the formation of the modified petal lip Furthermore I functionally characterized the PeSEP genes that are uniformly expressed in all floral organs in respects of protein-protein interaction and gene expression by using of yeast two-hybrid and VIGS PeSEPs themselves and possibly via regulating their downstream B-class genes involved in stimulating cell shape cellular ultra-structures floral pigmentation and cutin biosynthesis but inhibiting features of leaf-like structures to determine the development of orchid sepals petals and lip Together these studies have clarified the relationship of orchid B- and E-class MADS-box genes involved in the regulation of orchid floral organ identities and uncovered the critical roles in the obscure mystery of the orchid perianth morphogenesis
Date of Award2014 Aug 5
Original languageEnglish
SupervisorHong-Hwa Chen (Supervisor)

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