Proximal Distal Patterning During Maize Leaf Development

University Of Wyoming, Laramie WY

Investigators

Abstract

Intellectual Merit. Maize leaves consist of an upper photosynthetic blade separated at the ligule region from a lower enclosing sheath. Mutations that remove or alter the ligule region reduce the angle of the blade relative to the sheath, causing the leaves to extend upright. The ligule region thus helps to determine plant shape, and understanding how the structure develops will provide new tools for crop improvement. The ligule region is visible early in development at a restricted site, called a pre-ligule band, marked initially by increased cell division, cell expansion and localized gene expression. A fluorescent marker for an auxin carrier protein also localizes to the pre-ligule band, suggesting a role for hormone signaling in establishing the site. To understand the mechanism of ligule development, a collection of fluorescent markers will be used to map sequential changes in expression during early ligule development. Gene expression profiles in the pre-ligule region will be generated using laser capture microdissection followed by RNA sequencing. Three regions along the leaf axis will be captured, including the pre-ligule band itself, adjoining blade and subtending sheath tissue. Normal plants will be compared to mutants to identify expression changes on a genomic level when ligule growth is altered. Bioinformatic tools will be used to select candidate genes from these expression catalogs for further study. The selected genes will be validated by qRT-PCR, and their expression patterns studied by whole mount in situ hybridization. This research will identify the sequential and potentially interacting factors needed to make a ligule and will offer new genetic tools for manipulating leaf shape. Broader impacts. Leaf blade angle is an important agronomic trait in grain crops, such as maize. Plants with more upright leaves, caused by changes in ligule structure, may have higher crop yield if optimal photosynthesis can occur in less space. Maize ligule mutants are also excellent tools for teaching students about developmental genetics and genomics. The project will provide summer research opportunities specifically to Community College students and will develop Community College teaching modules in collaboration with education programs established at the University of Wyoming (UW). The teaching modules will be assessed using methods developed at the Science Math Teaching Center at UW and disseminated through UW to participating Community Colleges. Research data and teaching modules will be posted at a project website and made available to the research community and general public.