Tissue-Autonomous Promotion of Palisade Cell Development by Phototropin 2 in Arabidopsis

• Published in: The Plant cell 2011-10, Vol.23 (10), p.3684-3695
• Main Authors: Kozuka, Toshiaki, Kong, Sam-Geun, Doi, Michio, Shimazaki, Ken-ichiro, Nagatani, Akira
• Format: Article
• Language: English
• Subjects: Arabidopsis - cytology; Arabidopsis - genetics; Arabidopsis - growth & development; Arabidopsis - physiology; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Auxins; Chloroplasts; Chloroplasts - metabolism; Developmental biology; Environmental information; Epidermis; Gene Expression Regulation, Developmental - physiology; Gene Expression Regulation, Plant - physiology; Green Fluorescent Proteins; Leaves; Light; Light intensity; Light Signal Transduction - physiology; Mesophyll; Mesophyll cells; Mesophyll Cells - cytology; Mesophyll Cells - physiology; Mutation; Organ Specificity; Phosphoproteins - genetics; Phosphoproteins - metabolism; Photoreceptors; Phototropins - genetics; Phototropins - metabolism; Phototropism - genetics; Physiological regulation; Plant cells; Plant Epidermis - cytology; Plant Epidermis - genetics; Plant Epidermis - growth & development; Plant Epidermis - physiology; Plant Leaves - cytology; Plant Leaves - genetics; Plant Leaves - growth & development; Plant Leaves - physiology; Plants; Plants, Genetically Modified; Recombinant Fusion Proteins
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.111.085852

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.