Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2011 In search for maize florigen Xin Meng Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Part of the Cell and Developmental Biology Commons, and the Genetics and Genomics Commons Recommended Citation Meng, Xin, "In search for maize florigen" (2011). Graduate Theses and Dissertations. 10095. https://lib.dr.iastate.edu/etd/10095 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. In search for maize florigen by Xin Meng A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Major: Genetics Program of Study Committee: Erik W Vollbrecht, Co-major Professor Olga N. Danilevskaya, Co-major Professor David Hannapel Michael G. Muszynski Yanhai Yin Iowa State University Ames, Iowa 2011 Copyright © Xin Meng, 2011. All rights reserved. ii TABLE OF CONTENTS ABSTRACT ...................................................................................................................... iv CHAPTER ONE: GENERAL INTRODUCTION .........................................................1 Dissertation organization ..................................................................................................1 General introduction of Arabidopsis Flowering Locus T (FT) and its orthologs .............1 References ........................................................................................................................6 CHAPTER TWO: MOLECULAR CHARACTERIZATION OF MAIZE FT-LIKE ZCN GENES .......................................................................................................................9 Abstract ............................................................................................................................9 Introduction ......................................................................................................................9 Materials and methods ...................................................................................................13 Plant maerials and growth conditions .........................................................................13 Tissue collection .........................................................................................................14 Diurnal experiment .....................................................................................................14 Short day inductive experiment ..................................................................................15 RNA isolation, RT-PCR and quantitative RT-PCR ...................................................15 Tissue imaging............................................................................................................16 Arabidopsis T-DNA constructs and transformation ...................................................16 Statistical analysis ......................................................................................................16 Accession number ......................................................................................................16 Results ............................................................................................................................17 Survey of FT-like ZCN gene transcription in leaves of temperate and tropical lines under SD and LD photoperiods .................................................................................17 Responses of FT-like ZCN genes to a floral inductive SD treatment .........................18 Diurnal expression of three FT-like ZCN genes under SD and LD photoperiods ......20 Overexpression of FT-like ZCN genes in Arabidopsis ft mutants ..............................21 Discussion ......................................................................................................................22 FT-like ZCN genes display distinct expression patterns in the leaf of maize lines with different photoperiod sensitivities .............................................................................22 ZCN8 transcription is diurnally regulated in photoperiod-sensitive tropical lines but not in day-neutral lines ...............................................................................................24 Arabidopsis complementation experiment suggests that ZCN8, ZCN14 and ZCN15 are putative maize floral activators in which ZCN8 is the most promising one .........25 Acknowledgments ..........................................................................................................26 References ......................................................................................................................27 CHAPTER THREE: THE FT-LIKE ZCN8 GENE FUNCTIONS AS A MAIZE FLORAL ACTIVATOR IN THE id1-dlf1 GENETIC PATHWAY ..........................52 Abstract ..........................................................................................................................52 Introduction ....................................................................................................................52 Materials and methods ...................................................................................................55 Plant maerials and growth conditions .........................................................................55 Tissue collection .........................................................................................................56 RNA isolation, RT-PCR and quantitative RT-PCR ...................................................56 iii RNA in situ hybridization ..........................................................................................56 Yeast two-hybrid and GST pull-down assay ..............................................................56 Tissue imaging............................................................................................................57 Maize T-DNA constructs and transformation ............................................................57 Statistical analysis ......................................................................................................58 Accession number ......................................................................................................58 Results ............................................................................................................................58 Expression of FT-like ZCN genes in dlf1 and id1 late flowering mutants ................58 Interaction of FT-like ZCN proteins with the DLF1 protein ......................................60 RNA in situ hybridization of select FT-like ZCN genes in the leaf ..........................60 Flowering phenotype of maize transgenic plants ectopically expressing ZCN genes ..................................................................................................................62 Flowering phenotype of maize transgenic plants repressing ZCN8 mRNA expression ....................................................................................................................................63 Discussion ......................................................................................................................64 Genetic position of ZCN8 in the maize flowering pathway ......................................64 ZCN8 mRNA is expressed in the leaf phloem ............................................................65 ZCN8 induces early flowering when ectopically expressed in the shoot apex and delays flowering when constitutively repressed .........................................................66 ZCN8 is a maize floral activator with the potential florigenic function .....................66 Acknowledgments ..........................................................................................................69 References ......................................................................................................................69 CHAPTER FOUR: GENERAL CONCLUSIONS .......................................................96 A model integrating the autonomous and photoperiod pathways for flowering in maize ..........................................................................................................................96 Future work ....................................................................................................................97 Mobility of the ZCN8 protein .....................................................................................97 Identification of additional FT-like floral activators ..................................................97 References ..........................................................................................................................98 ACKNOWLEDGMENTS .............................................................................................101 iv ABSTRACT The mobile floral-promoting signal, florigen, is thought to consist of, in part, the FT protein named after the Arabidopsis thaliana gene Flowering locus T. FT is transcribed and translated in leaves and its protein moves via the phloem to the shoot apical meristem where it promotes the transition from vegetative to reproductive development.