Exclusion of plastid nucleoids and ribosomes from stromules in tobacco and Arabidopsis

• Published in: The Plant journal : for cell and molecular biology 2012-02, Vol.69 (3), p.399-410
• Main Authors: Newell, Christine A., Natesan, Senthil K. A., Sullivan, James A., Jouhet, Juliette, Kavanagh, Tony A., Gray, John C.
• Format: Article
• Language: English
• Subjects: Arabidopsis - cytology; Arabidopsis - genetics; Arabidopsis thaliana; Biochemistry, Molecular Biology; Biological and medical sciences; Biological Transport; Cellular biology; chloroplast; Chloroplasts; DNA; DNA, Chloroplast - metabolism; DNA, Plant - metabolism; Flowers & plants; Fluorescence; Fundamental and applied biological sciences. Psychology; Fusion protein; Genomics; Green fluorescent protein; Green Fluorescent Proteins - genetics; Green Fluorescent Proteins - metabolism; Hypocotyls; Lac repressor; Life Sciences; Microscopy, Confocal; Molecular and cellular biology; Molecular genetics; Nicotiana - cytology; Nicotiana - genetics; Nicotiana tabacum; Nucleoids; Nucleotide sequence; Plant biology; Plant physiology and development; Plants, Genetically Modified - cytology; Plants, Genetically Modified - genetics; plastid DNA; plastid nucleoid; plastid ribosome; Plastids; Plastids - metabolism; Ribonucleic acid; Ribosomal proteins; Ribosomes; Ribosomes - metabolism; RNA; Seedlings; stromule; Tobacco; Transformation, Genetic; Transgenic plants; Translation. Translation factors. Protein processing; Tubules
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313X.2011.04798.x

Summary Stromules are stroma‐filled tubules that extend from the surface of plastids and allow the transfer of proteins as large as 550 kDa between interconnected plastids. The aim of the present study was to determine if plastid DNA or plastid ribosomes are able to enter stromules, potentially permitting the transfer of genetic information between plastids. Plastid DNA and ribosomes were marked with green fluorescent protein (GFP) fusions to LacI, the lac repressor, which binds to lacO‐related sequences in plastid DNA, and to plastid ribosomal proteins Rpl1 and Rps2, respectively. Fluorescence from GFP–LacI co‐localised with plastid DNA in nucleoids in all tissues of transgenic tobacco (Nicotiana tabacum L.) examined and there was no indication of its presence in stromules, not even in hypocotyl epidermal cells, which contain abundant stromules. Fluorescence from Rpl1–GFP and Rps2–GFP was also observed in a punctate pattern in chloroplasts of tobacco and Arabidopsis [Arabidopsis thaliana (L.) Heynh.], and fluorescent stromules were not detected. Rpl1–GFP was shown to assemble into ribosomes and was co‐localised with plastid DNA. In contrast, in hypocotyl epidermal cells of dark‐grown Arabidopsis seedlings, fluorescence from Rpl1–GFP was more evenly distributed in plastids and was observed in stromules on a total of only four plastids (