Intracellular Distribution of Small Heat Stress Proteins in Cultured Cells of Lycopersicon peruvianum

Abstract

Summary In View Of The Contradictory Reports On The Nuclear Localization Of Small Heat Stress Proteins (Hsps) We Reinvestigated The Situation In Tomato Cell Cultures Using Three Different Methods: protein analysis of highly purified nuclei, immunofluorescence with isolated nuclei and immune electron microscopy. Results demonstrate the accumulation of HSP 17 in tomato cell nuclei under different heat stress and recovery conditions. The relative amount in nuclei parallels the synthesis and accumulation of HSP 17 in the cells. The distribution of HSP 17 between nucleoli, nucleoplasm, cytoplasmic heat stress granules and cytoplasm changes in the course of heat stress and recovery. The spectrum of the isoforms of the small HSPs is identical in whole cell extracts, purified nuclei and heat stress granules. Binding of HSP 17 to the nucleolar preribosomal material as well as to the cytoplasmic heat stress granules may indicate similar functions for protection of RNP material.