title: Tissue-autonomous promotion of palisade cell development by phototropin 2 in Arabidopsis.
abstract: Light is an important environmental information source that plants use to modify their growth and development. Palisade parenchyma cells in leaves develop cylindrical shapes in response to blue light; however, the photosensory mechanism for this response has not been elucidated. In this study, we analyzed the palisade cell response in phototropin-deficient mutants. First, we found that two different light-sensing mechanisms contributed to the response in different proportions depending on the light intensity. One response observed under lower intensities of blue light was mediated exclusively by a blue light photoreceptor, phototropin 2 (PHOT2). Another response was elicited under higher intensities of light in a phototropin-independent manner. To determine the tissue in which PHOT2 perceives the light stimulus to regulate the response, green fluorescent protein (GFP)-tagged PHOT2 (P2G) was expressed under the control of tissue-specific promoters in the phot1 phot2 mutant background. The results revealed that the expression of P2G in the mesophyll, but not in the epidermis, promoted palisade cell development. Furthermore, a constitutively active C-terminal kinase fragment of PHOT2 fused to GFP (P2CG) promoted the development of cylindrical palisade cells in the proper direction without the directional cue provided by light. Hence, in response to blue light, PHOT2 promotes the development of cylindrical palisade cells along a predetermined axis in a tissue-autonomous manner.
authors.affiliation: Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Kozuka
authors.forename: Sam-Geun
authors.initials: SG
authors.lastname: Kong
authors.forename: Michio
authors.initials: M
authors.lastname: Doi
authors.forename: Ken-ichiro
authors.initials: K
authors.lastname: Shimazaki
authors.forename: Akira
authors.initials: A
authors.lastname: Nagatani
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D049452:Green Fluorescent Proteins; D008027:Light; D055537:Light Signal Transduction / Q000502:physiology*; D058503:Mesophyll Cells / Q000166:cytology / Q000502:physiology*; D009154:Mutation; D009928:Organ Specificity; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D056949:Phototropins / Q000235:genetics / Q000378:metabolism; D018524:Phototropism / Q000235:genetics; D019441:Plant Epidermis / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D030821:Plants, Genetically Modified; D017346:Protein Serine-Threonine Kinases; D011993:Recombinant Fusion Proteins
chemical_list: D029681:Arabidopsis Proteins; C423903:PHOT2 protein, Arabidopsis; D010750:Phosphoproteins; D056949:Phototropins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; C103646:NPH1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases