Adaptation of an insect cell line of Spodoptera frugiperda to grow at 37 degrees C: Characterization of an endodiploid clone

Sf21 and Sf9 cell lines established from the lepidoptera Spodoptera frugipe rda do not display major induction of heat shock proteins when exposed to a temperature of 37 degrees C. After some months of adaptation at 37 degrees C we obtained two new cell lines, Sf21-HT and Sf9-HT, which have now been established for several years in our laboratory. The Sf9-HT line displays a slightly shorter doubling time at 37 degrees C than the wild type at 28 de grees C, but cell lethality gives rise to an earlier growth arrest. The com position of total lipid extract from heat-adapted cells reveals a higher sp hingomyelin to phosphatidylcholine ratio and a higher percentage of saturat ed fatty acids, which are expected for the lower membrane fluidity, require d for thermotolerance. The cell volume of Sf9-HT is doubled, and by flow cy tometry we showed that the DNA content is twice that in the parental cell l ine. Karyotypic examination of metaphasic cells achieved under epifluoresce nce microscopy revealed a doubled chromosome number in Sf9-HT.