Genetic control of early events in plant inflorescence development.

摘要

Recently, much has been learned about genes in Zea mays (maize) that affect floral organ specification and floral meristem identity. In contrast, only a modicum of information has been collected about maize genes acting prior to floral organ development. I therefore concentrated my studies on identifying and characterizing genes involved in the early events of maize inflorescence development. At the initiation of this project no clones had been identified for any mutants affecting inflorescence development. Because many members of the APETALA1 (AP1) clade of MADS-box genes have been shown to affect early decisions in dicot inflorescence development, I initiated a reverse genetics approach in hopes of identifying AP1-like clones that mapped to known maize mutants affecting inflorescence development. Simultaneously, I studied two maize mutants that affect early inflorescence meristem development, barrenstalk1 and branched silkless, which became the focus of phenotypic characterizations and gene cloning.; This dissertation contains a characterization of a family of maize genes having homology to the AP1-like MADS-box transcription factors in Arabidopsis. Six new MADS-box genes from maize belonging to the AP1 clade were cloned and characterized. Map locations failed to correlate any AP1-like maize MADS-box genes with known mutants affecting inflorescence and floral morphology.; Also included in this dissertation is a description of a recessive maize mutant called barrenstalk1 (ba1). The ba1 mutant makes the transition from vegetative to inflorescence development, but fails to make any lateral inflorescence branches or spikelets and has a central stalk devoid of any ears. Our study indicates that ba1 mutants are disrupted in the initiation of both vegetative and inflorescence axillary meristems.; I also collaborated with other members of the Schmidt lab in the cloning of the branched silkless (BD1) locus. We have shown that BD1 encodes a putative Ethylene Response Element Binding Protein/Apetala2-like transcription factor. As the final point of my dissertation, I report on my work describing closely related genes in Arabidopsis, one of which may be the true ortholog of BD1. These studies have allowed us to speculate about the mode of action of BD1 in maize and about the conservation of gene function in meristem development across distantly related species.