Proteolysis and Proteolytic Activities in the Acclimation to Stress: The Case of Sugar Starvation in Maize Root Tips

Abstract

The changes that stress induce in a plant may be either specific of the type of stress, or non-specific, ie, an effect of, or a response to, the stress situation itself. Several phenomena have been found to occur in a number of plant tissues under different stresses and are therefore of the non-specific type. This is the case of the production of toxic oxygen species (Foyer et al., 1991), the production of ethylene (Wang et al, 1990), increasing levels of polyamines (Flores, 1990), or the induction of heat-shockcognate proteins (Cabané et al., 1993) in response to temperature, osmotic, mineral or wounding stresses. It is not always clear whether these changes are part of an acclimation mechanism which would improve stress tolerance, or are symptoms of the cellular degradations caused by the environmental constraints. These observations however suggest that in spite of the diversity of stresses, similar mechanisms may be involved in the response to stress. In addition, modifications by stresses in the pattern of protein synthesis, in carbon allocation among plant organs, in maintenance respiration, or in developmental programs and senescence induction (Amthor and McCree, 1990) indicate that, at the same time as specific responses are induced, the metabolic background is profoundly modified. We believe that proteolysis is part of the common response system.