Reference "The Rice COLEOPTILE PHOTOTROPISM1 gene encoding an ortholog of Arabidopsis NPH3 is required for phototropism of coleoptiles and lateral translocation of auxin"

Reference ID

11489

Title

The Rice COLEOPTILE PHOTOTROPISM1 gene encoding an ortholog of Arabidopsis NPH3 is required for phototropism of coleoptiles and lateral translocation of auxin

Source

The Plant cell, 2005, vol. 17, pp. 103-115

Authors (4)

Haga-K	Takano-M
Neumann-R	Iino-M

Abstract

We isolated a mutant, named coleoptile phototropism1 (cpt1), from gamma-ray-
mutagenized japonica-type rice (Oryza sativa). This mutant 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 thaliana NPH3. These results, along with those for Arabidopsis,
demonstrate that NPH3/CPT1 is a key signal transduction component of higher
plant phototropism. 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-indole-3-acetic
acid 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.