Environmental influence on trehalogenesis in amoebae of the cellular slime molds

Abstract

Vegetative trehalase from Dictyostelium discoideum was purified to near homogeneity in a two-step procedure involving in situ enzymatic detection after SDS-PAGE and electroelution. The purified enzyme was used to quantify the levels of trehalose in a variety of dormant structures and in stressed amoebae of the cellular slime molds. It was found that the trehalose levels of vegetative amoebae of D. discoideum and Polysphondylium pallidum increased to levels, comparable to those seen during multicellular development, during heat shock (30 C) or cold shock (4 C) and decreased during recovery (23 C) from thermal stress. This accumulation of trehalose during thermal stress was not dependent on protein synthesis. Exposure to heavy metals, but not to agents that increased the osmotic potential of the surrounding medium, similarly affected trehalose levels in amoebae of D. discoideum. The activity and distribution of key enzymes involved in trehalose metabolism, trehalose-6-phosphate synthetase and trehalase, remained unchanged during thermal stress. The data support the view that trehalose plays a protective role in cells exposed to heat shock and other adverse conditions, in addition to being a storage form of energy and carbon during development.

Key Words:

• Dictyostelium
• osmotic shock
• Polysphondylium
• thermal shock
• trehalose