QUANTITATIVE AND QUALITATIVE ANALYSES OF PROTEIN SYNTHESIS DURING HEAT SHOCK IN THE MARINE DIATOM NITZSCHIA ALBA (BACILLARIOPHYCEAE)1

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Abstract
Protein synthesis in the diatom Nitzschia alba Lewin and Lewin was drastically altered when the cells were incubated at a supraoptimal temperaeture. Quantitatively, the overall protein synthesis was greatly suppressed as indicated by teh rate of [35S] methionine incorporation. The extent of suppression of protein synthesis was proportional to the severity of the heat‐shock treatment which was a combination of elevated temperature and treatment duration.The in viro synthesized proteins were also qualitativelty anlayzed by two‐dimensional gel electrophoresis. Dependeing on the treatment condition, a set of heat‐shock proteins (HSPs) were induced. They were best detected when the cells were subjected to shocks of 35°C for 60 min or 40°C for 10 min followed by a 60 min labelling at 30°C. The results revealed 16 HSps which had moluecular weights ranging from 24–94 kD and isoelectric points ranging from 5.50–7.10. Some of the HSps were identical in molelcular weights but with differeentr isoelectric points.The induction and accumulation of HSPs in Nitzschia alba were transitory. Prologned heat‐shock treatments resulted in a complete cessation of protein syntehsis and no further induction of HSPs. In all aspects, the heat shock response of diatoms was similar to that in higher plants such as soybean, maize and tobacco but differenet from most animal systems.

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