Abstract

Marisa Rosa, Jazmin Abraham Juarez, Michael Lewis, Brian St. Aubin, Alyssa Anderson, Katsutoshi Tsuda, Sarah Hake

Grass leaves provide a useful framework to investigate mechanisms that coordinate individual cell behavior with growth and differentiation. Their stereotypical shape includes a sheath that grips the stem, a blade that leans away from the stem, and a ligule region at the junction of blade and sheath. Prior to any visible differentiation of blade and sheath, a preligule band of dividing cells marks the position of the future ligule. Because the ligule occurs perpendicular to the cell files born from divisions, positional signals must guide the initiation and elaboration of the ligule. Using mutant analysis and laser capture microdissection, we have discovered that genes expressed at the ligule are also expressed in the boundary between lateral organs and the meristem. This result suggests a similarity between organ and ligule initiation. We are also investigating pleiotropic mutants with diminished or missing ligules. One is narrow odd dwarf, encoding a plasma membrane localized protein that may function in orchestrating cell wall behavior with external signals. Genes that are differentially expressed in nod mutants overlap with differentially expressed genes at the pre-ligule and with genes differentially expressed under drought stress. A second gene is liguleless narrow (lgn), which encodes a kinase. The mutant version of LGN shows a strong genotype by environment interaction. We have identified Sympathy for the Ligule (Sol), a QTL that rescues Lgn-R in hot weather. These pleiotropic mutants provide an inroad into exploring the connection between leaf development and stress response.