title: The signal transducer NPH3 integrates the phototropin1 photosensor with PIN2-based polar auxin transport in Arabidopsis root phototropism.
abstract: Under blue light (BL) illumination, Arabidopsis thaliana roots grow away from the light source, showing a negative phototropic response. However, the mechanism of root phototropism is still unclear. Using a noninvasive microelectrode system, we showed that the BL sensor phototropin1 (phot1), the signal transducer NONPHOTOTROPIC HYPOCOTYL3 (NPH3), and the auxin efflux transporter PIN2 were essential for BL-induced auxin flux in the root apex transition zone. We also found that PIN2-green fluorescent protein (GFP) localized to vacuole-like compartments (VLCs) in dark-grown root epidermal and cortical cells, and phot1/NPH3 mediated a BL-initiated pathway that caused PIN2 redistribution to the plasma membrane. When dark-grown roots were exposed to brefeldin A (BFA), PIN2-GFP remained in VLCs in darkness, and BL caused PIN2-GFP disappearance from VLCs and induced PIN2-GFP-FM4-64 colocalization within enlarged compartments. In the nph3 mutant, both dark and BL BFA treatments caused the disappearance of PIN2-GFP from VLCs. However, in the phot1 mutant, PIN2-GFP remained within VLCs under both dark and BL BFA treatments, suggesting that phot1 and NPH3 play different roles in PIN2 localization. In conclusion, BL-induced root phototropism is based on the phot1/NPH3 signaling pathway, which stimulates the shootward auxin flux by modifying the subcellular targeting of PIN2 in the root apex transition zone.
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
authors.forename: Yinglang
authors.initials: Y
authors.lastname: Wan
authors.forename: Jan
authors.initials: J
authors.lastname: Jasik
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Huaiqing
authors.initials: H
authors.lastname: Hao
authors.forename: Dieter
authors.initials: D
authors.lastname: Volkmann
authors.forename: Diedrik
authors.initials: D
authors.lastname: Menzel
authors.forename: Stefano
authors.initials: S
authors.lastname: Mancuso
authors.forename: František
authors.initials: F
authors.lastname: Baluška
authors.forename: Jinxing
authors.initials: J
authors.lastname: Lin
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism*; D008027:Light; D009154:Mutation; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D056949:Phototropins / Q000378:metabolism; D018524:Phototropism / Q000502:physiology*; D018517:Plant Roots / Q000378:metabolism / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D010750:Phosphoproteins; D056949:Phototropins; D017346:Protein Serine-Threonine Kinases; C400222:NPH3 protein, Arabidopsis; C117013:AT5G57090 protein, Arabidopsis; C103646:NPH1 protein, Arabidopsis