THE PLANT CELL, Vol 5, Issue 11 1611-1625, Copyright © 1993 by American Society of Plant Biologists
Development and Environmental Stress Employ Different Mechanisms in the Expression of a Plant Gene Family
E. J. DeRocher and H. J. Bohnert
Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721
Ribulose bisphosphate carboxylase small subunit (RbcS) genes in the common
ice plant, as in all higher plants, constitute a multigene family. We have
measured transcription activity and steady state mRNA levels of individual
members of the family, six RbcS genes, in the ice plant with emphasis on
the transition from C3 photosynthesis to Crassulacean acid metabolism
(CAM), which this plant undergoes during development and under
environmental stress. Four RbcS genes are differentially expressed in
leaves but are regulated in a coordinate fashion. A developmentally
engrained, sharp decline in the steady state mRNA levels, which is observed
during the juvenile-to-adult growth phase transition, coincides with the
time interval when the C3-to-CAM switch occurs. Developmental down
regulation of RbcS is due to down regulation of transcription. In contrast,
NaCl stress specifically affected RbcS transcript accumulation
post-transcriptionally, resulting in decreased RbcS mRNA levels.
Antagonistic regulatory programs are apparent in stress/stress relief
experiments. The results indicate complex controls, affecting both
transcriptional and post-transcriptional processes, that act differentially
during plant development, stress, and recovery from stress.
