Arabidopsis stromal 70-kDa heat shock proteins are essential for chloroplast development

Arabidopsis stromal 70-kDa heat shock proteins are essential for chloroplast development 70 kDa heat shock proteins (Hsp70s) act as molecular chaperones involved in essential cellular processes such as protein folding and protein transport across membranes. They also play a role in the cell’s response to a wide range of stress conditions. The Arabidopsis family of Hsp70s homologues includes two highly conserved proteins, cpHsc70-1 and cpHsc70-2 which are both imported into chloroplasts (Su and Li in Plant Physiol 146:1231–1241, 2008). Here, we demonstrate that YFP-fusion proteins of both cpHsc70-1 and cpHsc70-2 are predominantly stromal, though low levels were detected in the thylakoid membrane. Both genes are ubiquitously expressed at high levels in both seedlings and adult plants. We further show that both cpHsc70-1 and cpHsc70-2 harbour ATPase activity which is essential for Hsp70 chaperone activity. A previously described T-DNA insertion line for cpHsc70-1 (ΔcpHsc70-1) has variegated cotyledons, malformed leaves, growth retardation, impaired root growth and sensitivity to heat shock treatment. In addition, under stress conditions, this mutant also exhibits unusual sepals, and malformed flowers and sucrose concentrations as low as 1% significantly impair growth. cpHsc70-1/cpHsc70-2 double-mutants are lethal. However, we demonstrate through co-suppression and artificial microRNA (amiRNA) approaches that transgenic plants with severely reduced levels of both genes have a white and stunted phenotype. Interestingly, chloroplasts in these plants have an unusual morphology and contain few or no thylakoid membranes. Our data show that cpHsc70-1 and cpHsc70-2 are essential ATPases, have overlapping roles and are required for normal plastid structure. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Planta Springer Journals

Arabidopsis stromal 70-kDa heat shock proteins are essential for chloroplast development

Planta, Volume 232 (3) – May 28, 2010

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Publisher
Springer Journals
Copyright
Copyright © 2010 by Springer-Verlag
Subject
Life Sciences; Ecology; Forestry; Agriculture; Plant Sciences
ISSN
0032-0935
eISSN
1432-2048
D.O.I.
10.1007/s00425-010-1192-z
Publisher site
See Article on Publisher Site

Abstract

70 kDa heat shock proteins (Hsp70s) act as molecular chaperones involved in essential cellular processes such as protein folding and protein transport across membranes. They also play a role in the cell’s response to a wide range of stress conditions. The Arabidopsis family of Hsp70s homologues includes two highly conserved proteins, cpHsc70-1 and cpHsc70-2 which are both imported into chloroplasts (Su and Li in Plant Physiol 146:1231–1241, 2008). Here, we demonstrate that YFP-fusion proteins of both cpHsc70-1 and cpHsc70-2 are predominantly stromal, though low levels were detected in the thylakoid membrane. Both genes are ubiquitously expressed at high levels in both seedlings and adult plants. We further show that both cpHsc70-1 and cpHsc70-2 harbour ATPase activity which is essential for Hsp70 chaperone activity. A previously described T-DNA insertion line for cpHsc70-1 (ΔcpHsc70-1) has variegated cotyledons, malformed leaves, growth retardation, impaired root growth and sensitivity to heat shock treatment. In addition, under stress conditions, this mutant also exhibits unusual sepals, and malformed flowers and sucrose concentrations as low as 1% significantly impair growth. cpHsc70-1/cpHsc70-2 double-mutants are lethal. However, we demonstrate through co-suppression and artificial microRNA (amiRNA) approaches that transgenic plants with severely reduced levels of both genes have a white and stunted phenotype. Interestingly, chloroplasts in these plants have an unusual morphology and contain few or no thylakoid membranes. Our data show that cpHsc70-1 and cpHsc70-2 are essential ATPases, have overlapping roles and are required for normal plastid structure.

Journal

PlantaSpringer Journals

Published: May 28, 2010

References

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