Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

AKR2A-mediated import of chloroplast outer membrane proteins is essential for chloroplast biogenesis

Nature Cell Biology volume 10, pages 220–227 (2008)Cite this article

Abstract

In plant cells, chloroplasts have essential roles in many biochemical reactions and physiological responses1. Chloroplasts require numerous protein components, but only a fraction of these proteins are encoded by the chloroplast genome. Instead, most are encoded by the nuclear genome and imported into chloroplasts from the cytoplasm post-translationally2,3,4,5. Membrane proteins located in the chloroplast outer envelope membrane (OEM) have a critical function in the import of proteins into the chloroplast. However, the biogenesis of chloroplast OEM proteins remains poorly understood. Here, we report that an Arabidopsis ankyrin repeat protein, AKR2A, plays an essential role in the biogenesis of the chloroplast OEM proteins. AKR2A binds to chloroplast OEM protein targeting signals, as well as to chloroplasts. It also displays chaperone activity towards chloroplast OEM proteins, and facilitates the targeting of OEP7 to chloroplasts in vitro. AKR2A RNAi in plants with an akr2b knockout background showed greatly reduced levels of chloroplast proteins, including OEM proteins, and chloroplast biogenesis was also defective. Thus, AKR2A functions as a cytosolic mediator for sorting and targeting of nascent chloroplast OEM proteins to the chloroplast.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: AKR2A interacts specifically with chloroplast OEM proteins.
Figure 2: AKR2A interacts with OEP7 in vivo and prevents OEP7 aggregation.
Figure 3: RNAi(AKR2A)–akr2b plants have defects in OEM protein targeting and chloroplast development.
Figure 4: AKR2A binds to chloroplasts and enhances chloroplast targeting of OEP7.

Similar content being viewed by others

References

  1. Wise, R. R. & Hoober, J. K. The structure and function of plastids. (Springer, Dordrech, 2006).

    Book  Google Scholar 

  2. Chen, X. & Schnell, D. J. Protein import into chloroplasts. Trends Cell Biol. 9, 222–227 (1999).

    Article  CAS  Google Scholar 

  3. Keegstra, K. & Froehlich, J. E. Protein import into chloroplasts. Curr. Opin. Plant Biol. 2, 471–476 (1999).

    Article  CAS  Google Scholar 

  4. Bruce, B. D. Chloroplast transit peptides: structure, function and evolution. Trends. Cell Biol. 10, 440–447 (2000).

    Article  CAS  Google Scholar 

  5. Jarvis, P. Organellar proteomics: chloroplasts in the spotlight. Curr. Biol. 14, R317–R319 (2004).

    Article  CAS  Google Scholar 

  6. Schleiff, E. & Soll, J. Travelling of proteins through membranes: translocation into chloroplasts. Planta 211, 449–456 (2000).

    Article  CAS  Google Scholar 

  7. Schnell, D. J. & Hebert, D. N. Protein translocons: multifunctional mediators of protein translocation across membranes. Cell 112, 491–505 (2003).

    Article  CAS  Google Scholar 

  8. Constan, D., Patel, R., Keegstra, K. & Jarvis, P. An outer envelope membrane component of the plastid protein import apparatus plays an essential role in Arabidopsis. Plant J. 38, 93–106 (2004).

    Article  CAS  Google Scholar 

  9. Li, H. M., Moore, T. & Keegstra, K. Targeting of proteins to the outer envelope membrane uses a different pathway than transport into chloroplasts. Plant Cell 3, 709–717 (1991).

    Article  CAS  Google Scholar 

  10. Bauer, J. et al. Essential role of the G-domain in targeting of the protein import receptor atToc159 to the chloroplast outer membrane. J. Cell Biol. 159, 845–854 (2002).

    Article  CAS  Google Scholar 

  11. Smith, M. D., Hiltbrunner A., Kessler, F. & Schnell, D. J. The targeting of the atToc159 preprotein receptor to the chloroplast outer membrane is mediated by its GTPase domain and is regulated by GTP. J. Cell Biol. 159, 833–843 (2002).

    Article  CAS  Google Scholar 

  12. Tu, S. L. et al. Import pathways of chloroplast interior proteins and the outer-membrane protein OEP14 converge at Toc75. Plant Cell 16, 2078–2088 (2004).

    Article  CAS  Google Scholar 

  13. Hofmann, N. R. & Theg, S. M. Chloroplast outer membrane protein targeting and insertion. Trends Plant Sci. 10, 450–457 (2005).

    Article  CAS  Google Scholar 

  14. Lee, Y. J., Kim, D. H., Kim, Y.-W. & Hwang, I. Identification of a signal that distinguishes between the chloroplast outer envelope membrane and the endomembrane system in vivo. Plant Cell 13, 2175–2190 (2001).

    Article  CAS  Google Scholar 

  15. Lee, Y. J., Sohn, E. J., Lee, K. H., Lee, D. W. & Hwang, I. The transmembrane domain of AtToc64 and its C-terminal lysine-rich flanking region are targeting signals to the chloroplast outer envelope membrane. Mol. Cells 17, 281–291 (2004).

    CAS  PubMed  Google Scholar 

  16. Yan, J. Wang, J. & Zhang, H. An ankyrin repeat-containing protein plays a role in both disease resistance and antioxidation metabolism. Plant J. 29, 193–202 (2002).

    Article  CAS  Google Scholar 

  17. Chew, O. et al. A plant outer mitochondrial membrane protein with high amino acid sequence identity to a chloroplast protein import receptor. FEBS Lett. 557, 109–114 (2004).

    Article  CAS  Google Scholar 

  18. Jones, J. M., Morrell, J. C. & Gould, S. J. PEX19 is a predominantly cytosolic chaperone and import receptor for class 1 peroxisomal membrane proteins. J. Cell Biol. 164, 57–67 (2004).

    Article  CAS  Google Scholar 

  19. Yano, M., Terada, K. & Mori, M. AIP is a mitochondrial import mediator that binds to both import receptor Tom20 and preproteins. J. Cell Biol. 163, 45–56 (2003).

    Article  CAS  Google Scholar 

  20. Aoyama, T. & Chua, N. H. A glucocorticoid-mediated transcriptional induction system in transgenic plants. Plant J. 11, 605–612 (1997).

    Article  CAS  Google Scholar 

  21. Hamilton, A. J. & Baulcombe, D. C. A species of small antisense RNA in posttranscriptional gene silencing in plants. Science 286, 950–952 (1999).

    Article  CAS  Google Scholar 

  22. Kubis, S. et al. The Arabidopsis ppi1 mutant is specifically defective in the expression, chloroplast import, and accumulation of photosynthetic proteins. Plant Cell 15, 1859–1871 (2003).

    Article  CAS  Google Scholar 

  23. Jarvis, P. et al. An Arabidopsis mutant defective in the plastid general protein import apparatus. Science 282, 100–103 (1998).

    Article  CAS  Google Scholar 

  24. Bauer, J. et al. The major protein import receptor of plastids is essential for chloroplast biogenesis. Nature 403, 203–207 (2000).

    Article  CAS  Google Scholar 

  25. Tu, S. L. & Li, H. M. Insertion of OEP14 into the outer envelope membrane is mediated by proteinaceous components of chloroplasts. Plant Cell 12, 1951–1960 (2000).

    Article  CAS  Google Scholar 

  26. Li, H. M. & Chen, L. J. Protein targeting and integration signal for the chloroplastic outer envelope membrane. Plant Cell 8, 2117–2126 (1996).

    Article  CAS  Google Scholar 

  27. Wesley, S. V. et al. Construct design for efficient, effective and high-throughput gene silencing in plants. Plant J. 27, 581–590 (2001).

    Article  CAS  Google Scholar 

  28. Clough, S. J. & Bent, A. F. Floral dip: a simplified method for Agrobacterium-mediated transformation of Arabidopsis thaliana. Plant J. 16, 735–43 (1998).

    Article  CAS  Google Scholar 

  29. Lee, D. W. et al. Functional characterization of sequence motifs in the transit peptide of Arabidopsis small subunit of rubisco. Plant Physiol. 140, 66–83 (2006).

    Article  Google Scholar 

Download references

Acknowledgements

We thank H.-M. Li (Institute of Molecular Biology, Academia Sinica, Taiwan) for the anti-OEP7, anti-Toc33, anti-Toc34, anti-Toc75 and anti-Toc159 antibodies. The akr2b mutant (SALK T-DNA insertion line) was obtained from the Arabidopsis Biological Resources Center. This work was supported in part by a grant from Crop Functional Genomics Research Center (M107KG010003-07K0701-00330), Systems Biodynamics-National Core Research Center (R15-2004-033-05002-0) and the National Creative Research Initiatives program funded by the Ministry of Science and Technology, Korea and Core research fund of POSTECH.

Author information

Author notes

  1. Yong Jik Lee & Eun Ju Sohn

    Present address: Current address: Department of Cell Biology, University of California-Riverside, CA 92521, USA.,

  2. Wonsil Bae and Yong Jik Lee: These authors contributed equally to this work.

Authors and Affiliations

  1. Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, 790-784, Korea

    Wonsil Bae, Yong Jik Lee, Dae Heon Kim, Junho Lee, Soojin Kim, Eun Ju Sohn & Inhwan Hwang

Authors
  1. Wonsil Bae
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Yong Jik Lee
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Dae Heon Kim
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Junho Lee
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Soojin Kim
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Eun Ju Sohn
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Inhwan Hwang
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Inhwan Hwang.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Figures S1, S2, S3, S4, S5, s6, s7 and S8, Supplementary Table S1 and Supplementary Methods (PDF 690 kb)

Rights and permissions

Reprints and permissions

About this article

Cite this article

Bae, W., Lee, Y., Kim, D. et al. AKR2A-mediated import of chloroplast outer membrane proteins is essential for chloroplast biogenesis. Nat Cell Biol 10, 220–227 (2008). https://doi.org/10.1038/ncb1683

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/ncb1683

This article is cited by

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing