J Integr Plant Biol. ›› 2015, Vol. 57 ›› Issue (1): 93-105.DOI: 10.1111/jipb.12284

• Research Articles • Previous Articles     Next Articles

Blue-light-induced rapid chloroplast de-anchoring in Vallisneria epidermal cells

Yuuki Sakai1*, Shin-ichiro Inoue2, Akiko Harada3, Ken-ichiro Shimazaki4 and Shingo Takagi1   

  1. 1Department of Biological Sciences, Graduate School of Science, Osaka University, Osaka, Japan
    2Division of Biological Science, Graduate School of Science, Nagoya University, Aichi, Japan
    3Department of Biology, Osaka Medical College, Osaka, Japan
    4Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan
  • Received:2014-06-29 Accepted:2014-09-12 Published:2015-01-01
  • About author:*Correspondence: E-mail: yuukis0110@gmail.com

Abstract:

In the outer periclinal cytoplasm of leaf epidermal cells of an aquatic angiosperm Vallisneria, blue light induces “chloroplast de-anchoring”, a rapid decline in the resistance of chloroplasts against centrifugal force. Chloroplast de-anchoring is known induced within 1 min of irradiation with high-fluence-rate blue light specifically, preceding the commencement of chloroplasts migration toward the anticlinal cytoplasm. However, its regulatory mechanism has remained elusive, although pharmacological analysis suggested that a calcium release from intracellular calcium stores is necessary for the response. In search of the responsible photoreceptors, immunoblotting analysis using antibodies against phototropins demonstrated that cross-reactive polypeptides of 120-kDa exist in the plasma-membrane fraction prepared from the leaves. In vitro phosphorylation analysis revealed that 120-kDa polypeptides were phosphorylated by exposure to blue light in a fluence-dependent manner. The blue-light-induced phosphorylation activity was sensitive to a Ser/Thr kinase inhibitor, staurosporine, and unusually was retained at a high level for a long time in darkness. Furthermore, phototropin gene homologs (Vallisneria PHOTOTROPIN1 and PHOTOTROPIN2) expressed in leaves were isolated. We propose that calcium-regulated chloroplast de-anchoring, possibly mediated by phototropins, is an initial process of the blue-light-induced avoidance response of chloroplasts in Vallisneria.

 

Sakai Y, Inoue SI, Harada A, Shimazaki KI, Takagi S (2015) Blue‐light‐induced rapid chloroplast de‐anchoring in Vallisneria epidermal cells. J Integr Plant Biol 57: 93–105. doi: 10.1111/jipb.12284

Key words: Avoidance response of chloroplasts, Blue-light response, Chloroplast de-anchoring, Cytoplasmic calcium, Phototropin

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