THE PLANT CELL, Vol 4, Issue 6 657-665, Copyright © 1992 by American Society of Plant Biologists
Heat Shock Gene Expression Is Controlled Primarily at the Translational Level in Carrot Cells and Somatic Embryos
N. R. Apuya and J. L. Zimmerman
Department of Biological Sciences, University of Maryland Baltimore County, Baltimore, Maryland 21228
We have determined that the synthesis of heat shock proteins is regulated
ultimately at the translational level in heat-shocked carrot callus cells
and somatic embryos. Polysome analysis revealed that heat-shocked callus
cells do not translate most heat shock transcripts, which they abundantly
synthesize and accumulate. By contrast, heat-shocked globular embryos
accumulate low levels of heat shock mRNA but selectively translate more of
the heat shock mRNA molecules compared to callus cells and embryos of later
stages. The overall result of these different translational control schemes
is that undifferentiated callus cells and globular embryos synthesize
comparable levels of heat shock proteins even though they have large
differences in heat shock transcript levels.