[Expression analysis of 5 hsp70 genes in Tetrahymena thermophila]

Thirteen hsp70 genes with complete conserved domains were identified in Tetrahymena thermophila, and expression of five similar and non-intron hsp70 genes were analyzed. Under heat shock conditions of 37, 39 and 41oC, hsp70-2 mRNA had the highest relative expression level, suggesting it is closely related to heat shock. The basal level of constitutive T. thermophila hsp70-4 gene was high during 20 physiological/developmental stages of growth, starvation and conjugation, and it changed little upon exposure to heat shock: evidence that hsp70-4 is an hsc70 gene. The hsp70-4 cDNA is 2 208 bp long, and contains an open reading frame of 1 959 bp encoding 635 amino acids. Microarray data indicated that T. thermophila hsp70-3 gene probably participated in early starvation (0-12 h) stress and late conjugation (6-10 h) events, such as new macronuclear and micronuclear anlagen formation and old macronuclear elimination. However, hsp70-5 gene possibly participates in late starvation (12-15 h) stress and early conjugation (0-6 h) events such as micronuclear meiosis, micronuclear exchange and pronuclear fusion. Blast2GO indicated that they participated in dissimilar biological processes, suggesting hsp70-3 and hsp70-5 perform different functions.