Cell Fate Acquisition in Maize

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PI: Virginia Walbot (Stanford University)CoPI: W. Zacheus Cande (University of California, Berkeley; subawardee)Senior Personnel: Lisa Harper (University of California, Berkeley/USDA-ARS)As complex organisms develop, the body plan is established first, followed by the specification of organs, then their constituent tissues, and finally the functional cell types are designated. The regulation of cell fate acquisition occurs at many levels and is reflected in the gene expression and protein content within the cells and includes responses to external information such as hormones provided by surrounding tissues. Despite the importance of cell fate to final function, this process is difficult to study in complex tissues with many cell types and because the process is occurring asynchronously in many tissues. This project will exploit the five major cell types and their synchronous development within anthers to dissect cell fate in maize. Gene expression and protein changes that distinguish cells from their neighbors with a different fate will be defined. Mutants defective in cell fate acquisition at specific stages of anther development will be recovered by screening large collections of male-sterile mutants of maize established by prior work. The normal progression of cell fate acquisition will be elucidated by comparing cell expression patterns of normal to mutant anthers. Selected mutants will be described cytologically and by their pattern of gene expression. Finally, genes defining key mutant stages will be cloned to determine the nature of the gene product essential for normal cell fate acquisition. Data generated in the course of this project including microarray data and cytological descriptions of mutants will be made available through GEO (Gene Expression Omnibus (GEO) (http://www.ncbi.nlm.nih.gov/geo/) and through MaizeGDB (http://www.maizegdb.org). Biological resources will be available through the project and through the Maize Genetics Cooperation - Stock Center (http://maizecoop.cropsci.uiuc.edu). The lack of synchrony in pre-meiotic cells in most plants and animals has precluded deep analysis of the steps required for this particular fate decision. Consequently, new knowledge and insights from this project will illuminate steps in cell fate specification for the meiotic cells and surrounding somatic cells that will be of general significance in understanding both complex plant and animal development. To acquaint undergraduate students of agriculture focus with modern methods in plant genetics, the gene-tagging component of the project will be conducted at CalPoly-San Luis Obispo. Project senior personnel will acquaint students with the theory of transposon tagging in plants, and then train students to screen for male-sterile mutants in the field, to conduct genetic crosses for propagating mutants, to conduct allelism tests with previously identified mutants conferring similar phenotypes, to dissect anthers for analysis of gene expression, and to prepare DNA samples for the cloning of newly tagged mutant alleles.