2000 Fiscal Year Final Research Report Summary
Molecular mechanisms of phototropism of higher plants
| Project/Area Number |
10440242
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
植物生理
|
|---|
| Research Institution | Osaka City University |
|---|
Principal Investigator |
IINO Moritoshi Osaka City University, Graduate School of Science, 大学院・理学研究科, 助教授 (50176054)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
TARUI Yutaka Osaka City University, Graduate School of Science, 大学院・理学研究科, 講師 (00236770)
UEMATSU Chiyomi Osaka City University, Graduate School of Science, 大学院・理学研究科, 講師 (30232789)
TAKANO Makoto National Institute of Agrobiological Sciences, Department of Plant Biology, 生理機能研究グループ, チーム長 (20355754)
|
|---|
| Project Period (FY) |
1998 – 2000
|
| Keywords | phototropism / blue light responses / light signal transduction / coleoptiles / rice / auxin |
|---|
| Research Abstract |
The purpose of the proposed study was to resolve the light signaling mechanism underlying phototropism of higher plants. For this purpose, we undertook molecular genetic investigation using rice (Oryza sativa L) as an experimental material. Mutants impaired in phototropism of coleoptile phototropism were isolated from Y-ray-mutagenized japonica-type rice (cv. Nihonmasari). One of the isolated mutants, named coleoptile phototropism1 (cpt1), showed no coleoptile phototropism and severely reduced root phototropism after continuous stimulation. A map-based cloning strategy and transgenic complementation test were applied to demonstrate that a NPH3-like gene deleted in the mutant corresponds to CPT1. Phylogenetic analysis of putative CPT1 homologs of rice and related proteins indicated that CPT1 has an orthologous relationship with Arabidopsis NPH3. These results, along with those for Arabidopsis, demonstrate that NPH3/CPT1 is a key signal transduction component of higher plant phototropism
… More
. In an extended study with the cpt1 mutant, it was found that phototropic differential growth, is accompanied by a CPT1-independent inhibition of net growth. Kinetic investigation further indicated that a small phototropism occurs in cpt1 coleoptiles. This response, induced only transiently, was thought to be caused by the CPT1-independent growth inhibition. The ^3H-IAA applied to the coleoptile tip was asymmetrically distributed between the two sides of phototropically responding coleoptiles. However, no asymmetry was induced in cpt1 coleoptiles, indicating that lateral translocation of auxin occurs downstream of CPT1. It is concluded that the CPT1-dependent major phototropism of coleoptiles is achieved by lateral auxin translocation and subsequent growth redistribution. We further characterized another distinct mutant, coleoptile phototropism2 (cpt2). This mutant showed reduced coleoptile phototropism and normal root phototropism. Detailed analysis indicated that the mutant is specifically impaired in the ability to perceive and/or transduce light signal at the coleoptile tip. Map-based cloning of CPT2 gene is now in progress. Less
|
