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Published January 10, 2006 | Supplemental Material
Journal Article Open

MscS-like Proteins Control Plastid Size and Shape in Arabidopsis thaliana

Abstract

Background Mechanosensitive (MS) ion channels provide a mechanism for the perception of mechanical stimuli such as sound, touch, and osmotic pressure. The bacterial MS ion channel MscS opens in response to increased membrane tension and serves to protect against cellular lysis during osmotic downshock. MscS-like proteins are found widely in bacterial and archaeal species and have also been identified in fission yeast and plants. None of the eukaryotic members of the family have yet been characterized. Results Here, we characterize two MscS-like (MSL) proteins from Arabidopsis thaliana, MSL2 and MSL3. MSL3 can rescue the osmotic-shock sensitivity of a bacterial mutant lacking MS-ion-channel activity, suggesting that it functions as a mechanosensitive ion channel. Arabidopsis plants harboring insertional mutations in both MSL3 and MSL2 show abnormalities in the size and shape of plastids, which are plant-specific endosymbiotic organelles responsible for photosynthesis, gravity perception, and numerous metabolic reactions. MSL2-GFP and MSL3-GFP are localized to discrete foci on the plastid envelope and colocalize with the plastid division protein AtMinE. Conclusions Our data support a model wherein MSL2 and MSL3 control plastid size, shape, and perhaps division during normal plant development by altering ion flux in response to changes in membrane tension. We propose that MscS family members have evolved new roles in plants since the endosymbiotic event that gave rise to plastids.

Additional Information

© 2006 Elsevier Ltd. Received: October 10, 2005. Revised: November 11, 2005. Accepted: November 16, 2005. Published: January 9, 2006. The authors would like to acknowledge the Arabidopsis Knockout Facility at the University of Wisconsin, Madison for insertional mutants and the Arabidopsis Biological Resource Center at the Ohio State University for cDNAs. E.S.H was a Department of Energy (DOE) fellow of the Life Sciences Research Foundation. This work was also supported by the Colvin Fund of the California Institute of Technology and DOE FG02-88ER13873. We are grateful to Jean Edens for expertise in electron microscopy; Robert Spreitzer for antibodies to RBCL; Dennis Dougherty for MJF465 and pB10b-MscS; and Elison Blancaflor for pCAMBIA constructs. We also thank the members of the Meyerowitz lab, Paul Blount, and Doug Rees for critical reading of this manuscript.

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