Mosaic analysis of the dominant mutant, Gnarley1-R, reveals distinct lateral and transverse signaling pathways during maize leaf development

Maize leaves are organized into two major domains along the proximal-distal axis: a broad flat blade at the distal end of the leaf, and a narrow, thic kened sheath that encircles the stem. Between the blade and sheath are two wedge-shaped tissues called auricles, and the ligule, an epidermally derive d fringe. Members of the Knotted1 (Kn1) family of mutations change the shap e and position of both ligule and auricle, thus disturbing the overall patt ern of the leaf. Here we present the results of a mosaic analysis of Gnarle y1-R (GIII-R), which like members of the Kn1 family, affects the ligule and auricle, Gn1-R is distinct, however, in altering the dimensions of cells t hat make up sheath tissue. To gain insight into the Gn1-R phenotype, we per formed a mosaic analysis using X-ray induced chromosome Gn1-R leaves. These sectors allowed us to whether Gn1-R acts non-autonomously to influence adj acent cells. Most aspects of the Gn1-R phenotype, such as ligule position, inhibition of auricle development, and sheath thickness showed autonomy in the lateral dimension (leaf width). In contrast, all aspects of the Gn1-R p henotype were non-autonomous in the transverse dimension (leaf thickness), suggesting that signaling occurs between cell layers in the leaf. These res ults support a model for distinct signaling pathways along lateral versus t ransverse axes of a developing leaf.