CoPIs: Marja Timmermans (Cold Spring Harbor Laboratory), Gary Muehlbauer (University of Minnesota), Jianming Yu (Kansas State University), Diane Janick-Buckner, Jon Beck (Truman State University)
Collaborators Dan Nettleton (Iowa State University), Doreen Ware (USDA-ARS/Cold Spring Harbor Laboratory), David Micklos (Dolan DNA Learning Center)
The shoot apical meristem (SAM) is responsible for development of all above ground organs in the plant. Despite its essential roles during organogenesis, the molecular mechanisms regulating SAM function are poorly understood. Owing to a unique combination of biological advantages and genomic resources, maize is particularly well positioned for investigations of the genetic networks underlying SAM structure, function, and heterogeneity on a genomic scale. This project will address five specific objectives: (1) genetic characterization of candidate genes implicated in the regulation of SAM gene function and maize leaf patterning; (2) use of laser microdissection and transcript profiling to identify genes expressed during SAM initiation and development ; (3) identification of small RNA-controlled networks in SAM meristem function; (4) identification of quantitative trait loci (QTLs) controlling SAM architecture; and (5) identification of novel alleles (haplotypes) contributing to complex leaf traits using linkage-disequilibrium mapping.
Broader impacts of proposed research: These genomic analyses of SAM function will provide the intellectual framework for a strategy of scientific training and public outreach designed to disseminate an understanding and appreciation of plant science. Undergraduates at Truman State University, a small, public liberal arts institution in Kirksville (MO) will be trained to perform bioinformatic annotations of novel SAM genes, and carry out genetic, phenotypic, and molecular analyses of maize SAM mutants generated during this project. The Dolan DNA Learning Center at Cold Spring Harbor Laboratory will construct a public website/podcast entitled "Weed to Wonder" that will present the history of maize genetic research and celebrate its impact on human culture. All data generated during this project will be released to public databases include MaizeGDB (www.maizegdb.org) and Gramene (www.gramene.org), and seed harboring newly discovered maize mutations will be released for public distribution.
Intellectual Merit: Understanding the genetic factors controlling shoot meristem structure and function. The shoot apical meristem (SAM) is a pool of organ-forming stem cells that generates all the above ground structures in maize plants (shoots). This project generated quantitative data detailing gene expression programs during six stages of SAM development, from before the SAM is established, to its initiation and maturation. A gene expression atlas of functionally distinct regions of the SAM was generated as a tool toward understanding the molecular mechanisms of SAM function. Transcriptomic analyses (i.e. global gene expression) of two maize mutants with defects in leaf pattern formation were performed toward understanding fundamental mechanisms involved in making lateral organs (leaves) from the SAM. Domesticated maize harbors extremely genetic diversity, and this variation in gene sequence contributes to variations in plant morphology. Two distinct methodologies were employed to analyze the polygenic inheritance (traits controlled by multiple genes) of genes contributing to differences in SAM architecture, and differences in leaf morphology in diverse maize lines. SAM gene expression data from a diverse genetic population was generated and used to identify genes implicated to control the expression of other genes in maize shoots. This project has sponsored the curation and public release (Maize GDB) release of all transcriptomic, genomic, and genetic data generated. Twenty three publications have resulted from this award. Broader Impact: integration of research and education. Undergraduates from Truman State University (TSU) participated in genetic and molecular genetic analyses of SAM mutants identified by reverse genetics during this project. Also, approximately 30 undergraduate students enrolled in biology courses taught by Co-PI Janick-Buckner utilized SAM data and mutants as resources for the laboratory component of these courses. Collaborator David Micklos of the DNA Learning Center (DNALC) launched a prototype of the Weed to Wonder Internet site that tells the story of how human ingenuity transformed a common Mexican weed (teosinte) into a modern food wonder (maize). In 2011, Weed to Wonder was reconceived as a flexible "e-book" that can be ported as an Internet site, tablet-enabled application, or printable PDF. Using state-of-the-art Adobe InDesign and Flash software, we merged over 150 multimedia elements — including animations, photographs, and video interviews -- into an interactive National Geographic-style magazine. www.weedtowonder.org/.
