Poster: Cytoskeleton: Structure & Function

Abs # 1104: MUSTACHES is required for guard cell morphogenesis in Arabidopsis

Presenter:	Nadeau, Jeanette A, nadeau.5@osu.edu
Authors	Nadeau, Jeanette A (A)   Nakagawa, Tsuyoshi  (B)   Lucas, Jessica  (A)   Zhao, Liming  (A)   Heine, George  (A)   Sack, Fred D (A)
Affiliations:	(A): Ohio State University (B): Research Institute of Molecular Genetics, Shimane University

Stomata consist of two guard cells surrounding a pore and are necessary for gas exchange through the shoot epidermis. The genes involved in stomatal differentiation are largely unknown. Here we describe a locus, MUSTACHES (MUS) that is required for guard cell shape and pore formation. Guard cells arise from the symmetrical division of a progenitor cell followed by deposition of a lens-shaped cell wall thickening between the two cells. This area later separates to form the pore. At the same time, guard cells expand in a regulated fashion to attain the kidney shape necessary for stomatal valve action. Shape acquisition is associated with specialized radial microtubule arrays that focus at the developing pore site and that may guide the radial arrangement of cellulose microfibrils. In mustaches, the radial array of microtubules is distorted or absent in abnormal guard cells, yet these cells still express molecular and cytological markers of guard cell identity. Moreover, there are spatial defects in the localized deposition of cell wall material. These defects suggest that MUS plays a role in organized wall building, through targeted vesicular deposition and/or controlled deposition of cellulose microfibrils. Furthermore, the loss of symmetry between guard cell pairs in mus suggests that it participates in morphogenetic events coordinated between the cell pair. The recent discovery that MUS encodes a receptor kinase suggests a direct link between cell signaling and the spatial organization of the cytoskeleton controlling guard cell morphogenesis.