Water-soluble chlorophyll-binding proteins from Arabidopsis thaliana and Raphanus sativus target the endoplasmic reticulum body.
BACKGROUND
Non-photosynthetic chlorophyll (Chl) proteins called water-soluble Chl-binding proteins are distributed in Brassicaceae plants. Brassica oleracea WSCP (BoWSCP) and Lepidium virginicum WSCP (LvWSCP) are highly expressed in leaves and stems, while Arabidopsis thaliana WSCP (AtWSCP) and Raphanus sativus WSCP (RshWSCP) are highly transcribed in floral organs. BoWSCP and LvWSCP exist in the endoplasmic reticulum (ER) body. However, the subcellular localization of AtWSCP and RshWSCP is still unclear. To determine the subcellular localization of these WSCPs, we constructed transgenic plants expressing Venus-fused AtWSCP or RshWSCP.


RESULTS
Open reading frames corresponding to full-length AtWSCP and RshWSCP were cloned and ligated between the cauliflower mosaic virus 35S promoter and Venus, a gene encoding a yellow fluorescent protein. We introduced the constructs into A. thaliana by the floral dip method. We succeeded in constructing a number of transformants expressing Venus-fused chimeric AtWSCP (AtWSCP::Venus) or RshWSCP (RshWSCP::Venus). We detected fluorescence derived from the chimeric proteins using a fluorescence microscope system. In cotyledons, fluorescence derived from AtWSCP::Venus and RshWSCP::Venus was detected in spindle structures. The spindle structures altered their shape to a globular form under blue light excitation. In true leaves, the number of spindle structures was drastically reduced. These observations indicate that the spindle structure was the ER body.


CONCLUSIONS
AtWSCP and RshWSCP have the potential for ER body targeting like BoWSCP and LvWSCP.
Department of Biomolecular Science, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba, 274-8510, Japan. tshigekazu11@yahoo.co.jp.
Shigekazu
S
Takahashi
Department of Biomolecular Science, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba, 274-8510, Japan. 6313002a@nc.toho-u.ac.jp.
Kyoko
K
Aizawa
Department of Biomolecular Science, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba, 274-8510, Japan. nakayama@biomol.sci.toho-u.ac.jp.
Katsumi
K
Nakayama
Department of Biomolecular Science, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba, 274-8510, Japan. hsatoh@biomol.sci.toho-u.ac.jp.
Hiroyuki
H
Satoh
D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D017796:Caulimovirus / Q000235:genetics / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D061146:Chlorophyll Binding Proteins / Q000235:genetics* / Q000378:metabolism; D018548:Cotyledon / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D031224:Raphanus / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D008941:Spindle Apparatus / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure
D001426:Bacterial Proteins; D061146:Chlorophyll Binding Proteins; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; C054562:yellow fluorescent protein, Bacteria; D002734:Chlorophyll