Plant and Cell Physiology, 1987, Vol. 28, No. 6 975-985
© 1987
Article |
Heat Shock Response in Chlorella protothecoides1
2Department of Plant Sciences, School of Biological Sciences, Madurai Kamaraj University Madurai 625 021, India
3Department of Biotechnology, School of Biological Sciences, Madurai Kamaraj University University, Madurai 625 021, India
Chlorella cells grown under different nutritional conditions were transferred from the normal growth temperature of 25°C to elevated temperatures (30°C and 35°C), and the effect of heat shock (HS) on their protein synthesis was studied. The HS treatment caused a decrease in the incorporation of amino acids into some of the algal proteins. Unlike the above group of proteins, synthesis of another set of proteins with molecular masses 96, 92, 80, 74, 70, 68, 66, 44, and 19kDa were induced by HS. Interestingly, both the induction of HS proteins and recovery of the proteins which were inhibited by HS were very fast under appropriate conditions. Results also show that the photosynthetic activity was unaffected at 35°C for a period of 1 h. Furthermore, the synthesis of RuBP carboxylase was only marginally affected during HS at 35°C. Experiments using a transcription inhibitor and inhibitors of chloroplast and cytoplasmic protein synthesis showed that chloroplast protein synthesis was not significantly sensitive to HS treatment. However, cytoplasmic protein synthesis was severely affected. Actinomycin-D did not affect the induction of HS proteins. Hence HS response in Chlorella seems to be regulated to a large extent at the level of translation, rather than at the level of transcription. Furthermore, Chlorella HS proteins are the conserved proteins since proteins of similar molecular mass are induced in other organisms also during HS treatment.
1This paper is dedicated to Prof. S. Krishnaswamy on his sixty first birthday.
(Received January 20, 1987; Accepted May 20, 1987)
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