• 제목/요약/키워드: Chloroplast trafficking

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Targeting of Nuclear Encoded Proteins to Chloroplasts: a New Insight into the Mechanism

  • Lee, Yong-Jik;Kim, Yong-Woo;Pih, Kyeong-Tae;Hwang, Inhwan
    • 식물조직배양학회지
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    • 제27권5호
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    • pp.407-409
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    • 2000
  • Outer envelope membrane proteins of chloroplasts encoded by the nuclear genome are transported without the N-terminal transit peptide. Here, we investigated the targeting mechanism of AtOEP7, an Arabidopsis homolog of small outer envelope membrane proteins in vivo. AtOEP7 was expressed transiently in protoplasts or stably in transgenic plants as fusion proteins with GFP. In both cases AtOEP7:GFP was targeted to the outer envelope membrane when assayed under a fluorescent microscope or by Western blot analysis. Except the transmembrane domain, deletions of the N- or C-terminal regions of AtOEP7 did not affect targeting although a region closed to the C-terminal side of the transmembrane domain affected the targeting efficiency. Targeting experiments with various hybrid transmembrane mutants revealed that the amino acid sequence of the transmembrane domain determines the targeting specificity The targeting mechanism was further studied using a fusion protein, AtOEP7:NLS:GFP, that had a nuclear localization signal. AtOEP7:NLS:GFP was efficiently targeted to the chloroplast envelope despite the presence of the nuclear localization signal. Taken together, these results suggest that the transmembrane domain of AtOEP7 functions as the sole determinant of targeting specificity and that AtOEP7 may be associated with a cytosolic component during translocation to the chloroplast envelope membrane.

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Chrysanthemum Chlorotic Mottle Viroid-Mediated Trafficking of Foreign mRNA into Chloroplasts

  • Baek, Eseul;Park, Minju;Yoon, Ju-Yeon;Palukaitis, Peter
    • 식물병연구
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    • 제23권3호
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    • pp.288-293
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    • 2017
  • Chrysanthemum chlorotic mottle viroid (CChMVd) fused to the leader sequence of a reporter gene (mRFP) expressed transiently in agroinfiltrated Nicotiana benthamiana, was used to show that CChMVd can traffic into chloroplasts, thought to be the site of its replication. Fluorescence from mRFP was detected in chloroplasts, but only if the viroid transcription fusions were present, either from the full-length 400-nt CChMVd, or each of two partial fragments (nucleotides 125 to 2 and 231 to 372). The mRFP and its mRNA were detected by western blotting and RT-PCR, respectively, in tissue extracts of plants infiltrated by each fusion construct. Isolated chloroplasts were shown by RT-PCR to contain the RNA sequences of both CChMVd and mRFP, if both were present, but not the mRFP sequence in the absence of the viroid sequences. The results suggest that RNA trafficking was probably due to an RNA structure, and not a particular sequence, as discussed.