RESEARCH-PGR: Functional Genomics of Floral Meristem Termination in Maize

Fruits, grains and seeds account for most calories entering animal and human food systems. These vital commodities are produced by flowers that develop from plant stem cell tissues called meristems. Floral meristems (FMs) are unique in that they terminate after stem cells have been used up in the production of floral organs. Timing and proper completion of FM termination can have major impacts on fitness and yield. FM termination must be synchronized with the growing period in a tightly regulated process to ensure that complete sets of floral organs are produced. Fully formed flowers ultimately ensure reproductive success and produce food. This project will address fundamental questions in plant biology concerning floral patterning and meristem termination in maize (corn) by shedding light on an agronomically and economically crucial process in an indispensable U.S. and global crop species. A set of naturally occurring maize mutants defective in FM termination will be used to determine the genes and networks that underlie how normal flowers develop. The project will provide high-quality training and mentoring for trainees in genetics, genomics and developmental biology. A course-based undergraduate research experience will offer authentic hands-on research opportunities to students as part of their normal coursework. Annual science events will bring tangible activities related to floral biology and development to high school students interested in pursuing paths in STEM fields. Finally, an experiential learning module will be developed for the community to illustrate the importance of FMs in agriculture and the links between FM activity and floral morphology. Across billions of arable hectares worldwide, proper regulation of floral meristem (FM) termination can have major impacts on yield in crop plants, including maize. However, despite decades of research on transcriptional regulation of floral development and meristem determinacy in non-cereal model plants, extensive gene regulatory network (GRN) analyses or genome-wide chromatin maps of FM progression are lacking, leaving downstream genes and modes of regulation open for discovery. Furthermore, despite the fundamental importance of flower development to reproduction and yield, a comprehensive understanding about genes, genomic regions, and/or GRNs that regulate FM termination in maize and other cereal crops is lacking. This project will utilize a multi-omics approach with a core set of classical and newly characterized maize floral mutants to identify novel regulators of FM activity and elucidate the genomic circuitry that governs FM termination. The research will produce developmentally staged transcriptomes and determine the chromatin and cis-regulatory landscapes across maize floral development, information that will then be integrated to generate a transcriptional GRN. Future applications of these data could be leveraged to generate genome- and/or developmentally informed inducible synthetic factors to increase environmental flexibility during floral development. The work will generate an unprecedented resource for the plant science and breeding communities, further enabling functional plant genomics and crop improvement and linking basic research to applied outcomes in agriculture. Project outcomes will be disseminated broadly through publications and long-term, through public data and genetic resource repositories. 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.