Overexpression of AtHsp90.2, AtHsp90.5 and AtHsp90.7 in Arabidopsis thaliana enhances plant sensitivity to salt and drought stresses
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Three AtHsp90 isoforms, cytosolic AtHsp90.2, chloroplast-located AtHsp90.5, and endoplasmic reticulum (ER)-located AtHsp90.7, were characterized by constitutive overexpressing their genes in Arabidopsis thaliana. Both types of the transgenic plants overexpressing cytosolic and organellar AtHsp90s showed reduced tolerance to salt and drought stresses with lower germination rates and fresh weights, but improved tolerance to high concentration of Ca2+ comparing with the wild type plants. Transcriptional analysis of ABA-responsive genes, RD29A, RD22 and KIN2 under salt and drought stresses, indicated that the induction expression of these genes was delayed by constitutive overexpression of cytosolic AtHsp90.2, but was hardly affected by that of organellar AtHsp90.5 and AtHsp90.7. These results implied that Arabidopsis different cellular compartments-located Hsp90s in Arabidopsis might be involved in abiotic stresses by different functional mechanisms, probably through ABA-dependent or Ca2+ pathways, and proper homeostasis of Hsp90 was critical for cellular stress response and/or tolerance in plants.
KeywordsArabidopsis Calcium tolerance Heat shock protein 90 Stress sensitivity Signaling pathway
Cauliflower mosaic virus
Cognate form of Hsp
Heat shock protein
Mitogen-activated protein kinase
Reactive oxygen species
Unfolded protein response
We thank Dr. Walid Houry (University of Toronto, Canada) for providing us with polyclonal antibody against yeast Hsp82 protein. This work is supported by the National Natural Science Foundation of China (Grant No.30470352) and the National High Technology and Research Development Program of China (“863” project, Grant No. 2007AA091705).
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