title: NPH3- and PGP-like genes are exclusively expressed in the apical tip region essential for blue-light perception and lateral auxin transport in maize coleoptiles.
abstract: Phototropic curvature results from differential growth on two sides of the elongating shoot, which is explained by asymmetrical indole-3-acetic acid (IAA) distribution. Using 2 cm maize coleoptile segments, 1st positive phototropic curvature was confirmed here after 8 s irradiation with unilateral blue light (0.33 μmol m(-2) s(-1)). IAA was redistributed asymmetrically by approximately 20 min after photo-stimulation. This asymmetric distribution was initiated in the top 0-3 mm region and was then transmitted to lower regions. Application of the IAA transport inhibitor, 1-N-naphthylphthalamic acid (NPA), to the top 2 mm region completely inhibited phototropic curvature, even when auxin was simultaneously applied below the NPA-treated zone. Thus, lateral IAA movement occurred only within the top 0-3 mm region after photo-stimulation. Localized irradiation experiments indicated that the photo-stimulus was perceived in the apical 2 mm region. The results suggest that this region harbours key components responsible for photo-sensing and lateral IAA transport. In the present study, it was found that the NPH3- and PGP-like genes were exclusively expressed in the 0-2 mm region of the tip, whereas PHOT1 and ZmPIN1a, b, and c were expressed relatively evenly along the coleoptile, and ZmAUX1, ZMK1, and ZmSAURE2 were strongly expressed in the elongation zone. These results suggest that the NPH3-like and PGP-like gene products have a key role in photo-signal transduction and regulation of the direction of auxin transport after blue light perception by phot1 at the very tip region of maize coleoptiles.
authors: Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan.
authors: Satomi
authors: S
authors: Matsuda
authors: Tomomi
authors: T
authors: Kajizuka
authors: Akeo
authors: A
authors: Kadota
authors: Takeshi
authors: T
authors: Nishimura
authors: Tomokazu
authors: T
authors: Koshiba
mesh_terms: D001692:Biological Transport / Q000235:genetics / Q000502:physiology; D018548:Cotyledon / Q000378:metabolism* / Q000528:radiation effects; D007210:Indoleacetic Acids / Q000378:metabolism*; D008027:Light; D018524:Phototropism / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D003313:Zea mays / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D007210:Indoleacetic Acids; D010940:Plant Proteins