Analysis of the rice mutant dwarf and gladius leaf 1. Aberrant katanin-mediated microtubule organization causes up-regulation of gibberellin biosynthetic genes independently of gibberellin signaling

• Published in: Plant physiology (Bethesda) Vol. 138; no. 4; pp. 1982 - 1993
• Main Authors: Komorisono, M, Ueguchi-Tanaka, M, Aichi, I, Hasegawa, Y, Ashikari, M, Kitano, H, Matsuoka, M, Sazuka, T
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.08.2005; American Society of Plant Physiologists
• Subjects: adenosinetriphosphatase; Biological and medical sciences; Biosynthesis; brassinosteroids; Bundle sheath cells; Cell Biology and Signal Transduction; Cell growth; Cell physiology; Chromosome Mapping; Chromosomes, Plant; Cloning; dwarf and gladius leaf1 gene; dwarf cultivars; Epidermal cells; Fundamental and applied biological sciences. Psychology; Gene expression regulation; Gene Expression Regulation, Plant; Genes, Plant; gibberellic acid; Gibberellins; Gibberellins - biosynthesis; katanin; Leaves; microtubule-associated proteins; Microtubules; Microtubules - genetics; Microtubules - physiology; Molecular and cellular biology; molecular cloning; molecular sequence data; mutants; Mutation; nucleotide sequences; Oryza - genetics; Oryza - physiology; Oryza sativa; Phenotype; phenotypic variation; Phylogeny; plant biochemistry; plant genetics; Plant Leaves - anatomy & histology; Plant Leaves - physiology; plant morphology; plant proteins; Plant Proteins - biosynthesis; Plants; Rare species; Rice; Signal transduction; Signal Transduction - genetics; Signal Transduction - physiology; Steroids; Up regulation; Oryza sativa; Monocotyledones; Brassinosteroid; Gene; Gramineae; Angiospermae; Gibberellin; Spermatophyta; Plant leaf; Microtubule; Mutation
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.105.062968

Molecular genetic studies of plant dwarf mutants have indicated that gibberellin (GA) and brassinosteroid (BR) are two major factors that determine plant height; dwarf mutants that are caused by other defects are relatively rare, especially in monocot species. Here, we report a rice (Oryza sativa) dwarf mutant, dwarf and gladius leaf 1 (dgl1), which exhibits only minimal response to GA and BR. In addition to the dwarf phenotype, dgl1 produces leaves with abnormally rounded tip regions. Positional cloning of DGL1 revealed that it encodes a 60-kD microtubule-severing katanin-like protein. The protein was found to be important in cell elongation and division, based on the observed cell phenotypes. GA biosynthetic genes are up-regulated in dgl1, but the expression of BR biosynthetic genes is not enhanced. The enhanced expression of GA biosynthetic genes in dgl1 is not caused by inappropriate GA signaling because the expression of these genes was repressed by GA3 treatment, and degradation of the rice DELLA protein SLR1 was triggered by GA3 in this mutant. Instead, aberrant microtubule organization caused by the loss of the microtubule-severing function of DGL1 may result in enhanced expression of GA biosynthetic genes in that enhanced expression was also observed in a BR-deficient mutant with aberrant microtubule organization. These results suggest that the function of DGL1 is important for cell and organ elongation in rice, and aberrant DGL1-mediated microtubule organization causes up-regulation of gibberellin biosynthetic genes independently of gibberellin signaling.