ANGUSTIFOLIA: A Dual Function Microtubule Regulator?

ANGUSTIFOLIA (AN) is a regulator of leaf development, including the epidermis of the leaves and the leaf hairs (trichomes). Arabidopsis thaliana carrying mutations in an exhibit shorter, thicker leaves and defective trichome branching. Two groups analyzed these defects in more detail and cloned the AN gene. Kim et al. showed that cortical microtubules (MTs) were disorganized in leaf epidermis and Folkers et al. showed that the density distribution of MTs was altered in trichomes. The AN gene encodes a protein that appears to be a member of the CtBP and BARS family. These proteins are named for their dual functions: COOH-terminal-binding proteins (CtBP), which were originally identified as transcriptional repressors, and brefeldin A adenosine diphosphate (ADP)-ribosylated substrates (BARS), which are implicated in Golgi dynamics. Kim et al. showed that the expression of several genes was increased in An mutants, consistent with a function of transcriptional repressor. Folker et al. found a genetic interaction between AN and the Arabidopsis kinesin motor protein ZWICHEL. This interaction was confirmed by a yeast two-hybrid assay. Thus, the plant CtBP and BARS protein, AN, may also be a dual function protein. G.-T. Kim, K. Shoda, T. Tsuge, K.-H. Cho, H. Uchimiya, R. Yokoyama, K. Nishitani, H. Tsukaya, The ANGUSTIFOLIA gene of Arabidopsis , a plant CTBP gene, regulates leaf-cell expansion, the arrangement of cortical microtubules in leaf cells and expression of a gene involved in cell-wall formation. EMBO J. 21 , 1267-1279 (2002). [Abstract] [Full Text] U. Folkers, V. Kirik, U. Schöbinger, S. Falk, S. Krishnakumar, M. A. Pollock, D. G. Oppenheimer, I. Day, A. R. Raddy, G. Jürgens, M. Hülskamp, The cell morphogenesis gene ANGUSTIFOLIA encodes a CtBP/BARS-like protein and is involved in the control of the microtubule cytoskeleton. EMBO J. 21 , 1280-1288 (2002). [Abstract] [Full Text]