Specific heat shock proteins are transported into chloroplasts

AUTOR(ES)

Vierling, Elizabeth

RESUMO

We demonstrate that in three plant species—soybean, pea, and corn—certain nuclear-encoded heat shock proteins are transported into chloroplasts. In vitro translation products of poly(A)-RNA from control or heat-shocked plants were incubated with isolated intact pea chloroplasts and differences in the profile of imported proteins were analyzed. In all three species, abundant polypeptides between 21 and 27 kDa are present in the heat shock sample and absent in the controls. These polypeptides are protected from trypsin and chymotrypsin digestion after their import into chloroplasts and are recovered primarily with the soluble chloroplast protein fraction. Chloroplasts isolated from pea or corn leaves labeled in vivo at heat shock temperatures, but not at normal growth temperatures, contain the same polypeptides observed in vitro. Synthesis of the heat shock polypeptides can be inhibited in vivo by cycloheximide but not by chloramphenicol, further indicating they are products of cytoplasmic protein synthesis. The in vitro transport experiments demonstrate that synthesis of the chloroplast-localized heat shock proteins results from heat-induced accumulation of the corresponding poly(A)-RNAs. The same mRNAs are also produced in response to heat shock by a nonphotosynthetic tissue, the etiolated soybean hypocotyl.

Documentos Relacionados

• A heat shock protein localized to chloroplasts is a member of a eukaryotic superfamily of heat shock proteins.
• Efficient in vitro import of a cytosolic heat shock protein into pea chloroplasts
• Heat shock proteins are methylated in avian and mammalian cells.
• Two mammalian heat shock proteins, HSP90 and HSP100, are actin-binding proteins.
• Tissue-Type-Specific Heat-Shock Response and Immunolocalization of Class I Low-Molecular-Weight Heat-Shock Proteins in Soybean.