Identification of GhLFY functions and its transcriptional co-regulators during the development of capitulum in Gerbera hybrida

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Title: Identification of GhLFY functions and its transcriptional co-regulators during the development of capitulum in Gerbera hybrida
Author: Zhang, Teng
Contributor: University of Helsinki, Faculty of Agriculture and Forestry, Department of Agricultural Sciences
Publisher: Helsingin yliopisto
Date: 2015
Language: eng
Thesis level: master's thesis
Discipline: Växtproduktionsvetenskap
Plant Production Science
Abstract: The architecture of inflorescence refers to the spatio-temporal arrangement of flowers on the reproductive branches. Flowering plants have evolved great diversity in such branching systems. Among which, the showy capitulum type inflorescence in the large Compositae (Asteraceae) species is regarded as a prerequisite factor for their wide spreading around the world. Different from the simple raceme and cyme, capitulum compresses hundreds of individual florets on its receptacle, but overall resembles a single, solitary flower. The ontogeny of capitulum also bears resemblance to a single flower, with regard to the meristem determinacy, floral sequence and histological configurations. Recent molecular studies have revealed that a plant specific transcription factor LEAFY (LFY), is required for both the floral initiation and floral patterning, the two essential steps to form an inflorescence. The thesis elaborates Gerbera hybrida as a model to elucidate functions of the LFY ortholog during the development of inflorescence/flower in a capitulum background. In addition to the conserved functions in regulating floral meristem identity and floral patterning, three specified functions were revealed by transgenic Gerbera with down-regulated expression of GhLFY. Firstly, GhLFY is involved in the regulating the floral initiation of marginal ray florets. Down regulation of GhLFY resulted the marginal ray florets revert into a branching patterm that shown on the capitulum of Calyceraceae, the close relatives of Asteraceae. Secondly, the determinacy of IM is disrupted when GhLFY loses its functions, suggesting that GhLFY may function at both the flower and inflorescence interfaces. Thirdly, different flower types show specific responses to GhLFY down-regulation in floral patterning, indicating that there exist a potential genetic gradient among different flower types. At protein level, the LFY functions are specified by formation of versatile protein complexes with its transcriptional co-regulators. In Gerbera, GhLFY proteins tend to form homodimers and they were also capable to interact with a conserved transcriptional co-regulator, the UNUSUAL FLORAL ORGANS (UFO) ortholog GhUFO. Taken advantage of the forward Y2H library screening, 6 additional proteins were identified to interact with GhLFY, including several novel potential co-regulators of LFY that has not yet been identified in other species. Additionally, a bimolecular fluorescence complementation assay (BiFC) was optimized to verify the GhLFY self-interaction in planta.
Subject: Infloresence architecture
meristem identity genes
capitulum patterning

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