第1107回生物科学セミナー
Role of DESIGUAL1 and auxin in bilateral symmetry of Arabidopsis leaves
José Luis Micol（Instituto de Bioingeniería, Universidad Miguel Hernández）
2016年07月06日(水) 14:55-16:40 理学部2号館 講堂
Most living beings exhibit some form of symmetry; however, there is a dearth of mutations affecting bilateral symmetry in all biological systems. This lack of mutations has hampered genetic analysis of bilateral symmetry in multicellular organisms, particularly plants. To examine the regulation of symmetry and other facets of leaf development, we screened 19,850 Arabidopsis lines from the Salk homozygous T-DNA collection, and found 706 leaf mutants1. Only one of these mutants exhibited defects in bilateral symmetry; we named this mutant desigual1-1 (deal1-1).
Arabidopsis has bilaterally symmetric leaves with interspersed marginal lobes and indentations along the margin. Several overlapping regulatory pathways establish these marginal features; these pathways involve feedback loops of auxin, the PIN-FORMED1 (PIN1) auxin efflux carrier, and the CUP-SHAPED COTYLEDON2 (CUC2) transcriptional regulator2,3.
The deal1 mutants have randomly asymmetric leaves that fail to acquire symmetry in the early stages of leaf primordium development, but instead form ectopic lobes and sinuses. In the leaves of deal1 mutants, improper regulation of cell division (simultaneous over- and under-proliferation) along the organ margins alters bilateral symmetry during the primordium stage. Auxin maxima are mislocalized at the margins of expanding deal1 leaves and this asymmetry can be enhanced by treatment with the polar auxin transport inhibitor 1-N-naphthylphthalamic acid or alleviated by treatment with the synthetic auxin 1-naphthaleneacetic acid. Among other defects, deal1 mutants show aberrant recruitment of marginal cells expressing properly polarized PIN1, resulting in misplaced auxin maxima. Normal PIN1 polarization requires CUC2 expression and CUC2 genetically interacts with DEAL1; DEAL1 also affects CUC2 expression in the leaf primordium margin. DEAL1, a protein of unknown molecular function, localizes to the endoplasmic reticulum membrane and functions in the leaf, acting partially redundantly with its two closest paralogs. DEAL1 also participates in flower development, revealing that this gene has diverse functions in plant morphogenesis.
1.- Wilson-Sánchez, D., Rubio-Díaz, S., Muñoz-Viana, R., Pérez-Pérez, J.M., Jover-Gil, S., Ponce, M.R., and Micol, J.L. (2014). Plant Journal 79, 878-891.
2.- Bilsborough, G.D., Runions, A., Barkoulas, M., Jenkins, H.W., Hasson, A., Galinha, C., Laufs, P., Hay, A., Prusinkiewicz, P., and Tsiantis, M. (2011). Proceedings of the National Academy of Sciences USA 108, 3424-3429.
3.- Kasprzewska, A., Carter, R., Swarup, R., Bennett, M., Monk, N., Hobbs, J.K., and Fleming, A. (2015). Plant Journal 83, 705-718.
