Plant Molecular Biology

, Volume 67, Issue 4, pp 323–334

Complexity of Hsp90 in organelle targeting

  • Constantinos Prassinos
  • Kosmas Haralampidis
  • Dimitra Milioni
  • Despina Samakovli
  • Konstantinos Krambis
  • Polydefkis Hatzopoulos
Article

DOI: 10.1007/s11103-008-9322-8

Cite this article as:
Prassinos, C., Haralampidis, K., Milioni, D. et al. Plant Mol Biol (2008) 67: 323. doi:10.1007/s11103-008-9322-8

Abstract

Heat shock protein 90 (Hsp90) is an abundant and highly conserved molecular chaperone. In Arabidopsis, the Hsp90 gene family consists of seven members. Here, we report that the AtHsp90-6 gene gives rise to two mRNA populations, termed AtHsp90-6L and AtHsp90-6S due to alternative initiation of transcription. The AtHsp90-6L and AtHsp90-6S transcription start sites are located 228 nucleotides upstream and 124 nucleotides downstream of the annotated translation start site, respectively. Both transcripts are detected under normal or heat-shock conditions. The inducibility of AtHsp90-6 mRNAs by heat shock implies a potential role of both isoforms in stress management. Stable transformation experiments with fusion constructs between the N-terminal part of each AtHsp90-6 isoform and green fluorescent protein indicated import of both fusion proteins into mitochondria. In planta investigation confirmed that fusion of the AtHsp90-5 N-terminus to green fluorescent protein (GFP) did result in specific chloroplastic localization. The mechanisms of regulation for mitochondria- and plastid-localized chaperone-encoding genes are not well understood. Future work is needed to address the possible roles of harsh environmental conditions and developmental processes on fine-tuning and compartmentalization of the AtHsp90-6L, AtHsp90-6S, and AtHsp90-5 proteins in Arabidopsis.

Keywords

Alternative transcriptionChloroplastsHeat shockHsp90MitochondriaTargeting

Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  • Constantinos Prassinos
    • 1
  • Kosmas Haralampidis
    • 2
  • Dimitra Milioni
    • 1
  • Despina Samakovli
    • 1
  • Konstantinos Krambis
    • 1
    • 3
  • Polydefkis Hatzopoulos
    • 1
  1. 1.Laboratory of Molecular Biology, Agricultural Biotechnology DepartmentAgricultural University of AthensAthensGreece
  2. 2.Molecular Plant Development Laboratory, Faculty of Biology, Department of BotanyUniversity of AthensAthensGreece
  3. 3.Virginia Bioinformatics InstituteBlacksburgUSA