Translation activity under ultraviolet radiation and temperature stress in the cyanobacterium Nostoc sp.

Abstract

Stress proteins are known to be expressed as a response to a number of external factors including ultraviolet radiation (UVR). In the present work, the translation activity under elevated temperature and UVR stress has been studied in a Nostoc species isolated from an Andean lake (Cuzco, Peru). The viability of the cells is not equally affected by the two stresses; while 84% of the cells survive exposure to 42°C, the viability after a UVR dose of 50 kJ m −2 is 40%. Induction of the heat response prior to UV irradiation does not improve cell survival of Nostoc cells subjected to UVR. A group of nine heat-shock proteins (hsps) is induced by the temperature shift from 18 to 50°C (hsp 90, hsp 75, hsp 69, hsp 67, hsp 45, hsp 22, hsp 20, hsp 18 and hsp 16). In contrast to heat stress which enhances protein synthesis, UVR seriously impairs translation activity in Nostoc sp. A 18 kDa protein is induced by UV-B.