This action funds an NSF National Plant Genome Initiative Postdoctoral Research Fellowship in Biology for FY 2019. The fellowship supports a research and training plan in a host laboratory for the Fellow who also presents a plan to broaden participation in biology. The title of the research and training plan for this fellowship to Dr. Daniel Blaine Marchant is "Transcriptional Regulation and Evolution of the Maize Tapetum". The host institution for the fellowship is Stanford University and the sponsoring scientist is Dr. Virginia Walbot.
Understanding anther development is fundamental to plant biology from both applied and basic science perspectives. As the source of pollen and male gametes, anthers are a key variable in controlled crop breeding and hybrid seed production. As of yet, the cues and pathways that permit the alternation from a non-reproductive somatic cell to a reproductive germinal cell in plants are poorly understood. The overarching goal of the research is to use maize anthers and state-of-the-art technologies and genetic resources to address questions and provide new insights into the cellular and genetic regulation of anther development and flowering plant reproduction through evolution. Maize is the ideal primary system for this study because each maize plant has separate male and female organ systems, hundreds of developmentally synchronous anthers per plant, and there exists a large collection of male-sterile and female-fertile mutants. Broader impacts include expanding the organismal and evolutionary knowledge base of plant scientists by training and mentoring of students and by building a "Plant Model Systems Living Collection" in which specimens of the most widely used plant genomics model systems will be housed and maintained at Stanford University. Public access will be enhanced by the availability of learning resources such as web-based manuals providing information on the propagation, natural history and evolution, and anatomy of each species as well as on methods routinely used in plant research such as tissue culture and DNA/RNA extraction. Training objectives include acquiring expertise with new transcriptomic and genomics methods, and bioinformatics tools.
The de novo differentiation and development of somatic cells into reproductive germ cells is of the upmost importance for plant reproduction as plants do not have established germlines unlike sexual animals. Understanding the genetic cues of the cell layers that regulate sporogenesis in anthers is therefore fundamental to plant biology, but also to agriculture because controlled pollen production underlies hybrid seed production of most crops. Next-generation sequencing and micro-scale RNA isolation have completely altered our knowledge of how anther cell layers differentiate in preparation for meiosis and the cues by which these processes are regulated. This study will expand upon those studies, delving further into the genetic regulation and hierarchies of the cell layers throughout anther sporogenesis with a focus on the tapetum, the cell layer surrounding the germinal cells. State of the art techniques and resources will be implemented to analyze this specific cell layer first in maize, then in taxa across vascular plants. Specific aims include: 1) identifying tapetum-specific and differentially expressed genes and transcription factors across development in wildtype and tapetum-related male-sterile genotypes; 2) developing and implementing two new protocols for investigating the tapetum at the single cell scale to address questions regarding cellular synchroneity within an anther, the precise developmental stages of the tapetum, and sub-cellular localization of transcripts in a comparative techniques framework; and, 3) providing new insights into the evolutionary conservation of the tapetum genetic hierarchy and tapetum-specific genes across vascular plants. The results of this research will be disseminated at the annual International Plant and Animal Genome (PAG) and Maize Genetics Conferences, and through publications in high profile scientific journals. Sequence data will be made publicly available through the NCBI Sequence Read Archive (SRA) and through Gramene and MaizeGDB. In addition, the learning resources produced for the "Plant Model Systems Living Collection" will be available online through the Stanford Biology Department website.
Keywords: anthers, maize, tapetum, development, meiosis, pollen, sporogenesis, evolution
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
