An ancient developmental induction: heat-shock proteins induced in sporulation and oogenesis.

Every eukaryotic and prokaryotic organism tested to date synthesizes a small number of heat-shock proteins in response to heat and other forms of stress. A particular pattern of heat-shock gene expression was observed during ascospore development in Saccharomyces: heat-shock proteins hsp26 and hsp84 were strongly induced nor inducible by heat shock. Instead, two proteins related to hsp70 were induced. A strikingly similar pattern of expression occurs during oogenesis in Drosophila, suggesting that it may be one of the earliest developmental pathways to evolve in eukaryotic cells.