Temperature-induced stress on growth and expression of hsp in freshwater alga Scenedesmus quadricauda.

OBJECTIVE To investigate the impact of various levels of sublethal temperature (26 degrees C, 31 degrees C, 33 degrees C, 36 degrees C, and 39 degrees C) on growth and heat shock protein (hsp) expression in freshwater green alga Scenedesmus quadricauda. METHODS Impact of selected levels of temperature on growth rate (based on optical density), population count, chlorophyll-a and biomass of the alga was evaluated in artificial growth medium for 19 days. To determine the induction of hsp in the alga, it was exposed to selected temperature levels for 3 h and further kept for 6 h at culturing condition at 26 degrees C. Induction of hsp was confirmed by immuno-detection followed by SDS-polyacrylamide gel electrophoresis. RESULTS The selected growth parameters such as growth rate, population count, chlorophyll-a and biomass were reduced significantly (P < 0.001) at 39 degrees C. However, hsp 70 expression was observed only at 39 degrees C. CONCLUSION Temperature up to 36 degrees C may be considered as the limit of safe exposure for thermal stress for the alga Scenedesmus quadricauda.