Temporal co-ordination of macroschizont and merozoite gene expression during stage differentiation of Theileria annulata

The bovine parasite. Theileria annulata has a complex life-cycle involving the expression and repression of genes during development of its morphologi cally distinct life-cycle stages. In order to detail the molecular events t hat occur during differentiation of the intracellular multinucleate macrosc hizont to the extra-cellular uninucleate merozoite. we have isolated two ge nes. Tash1 and Tash2 which are differentially expressed during differentiat ion. Nuclear run on data show that Tash1 gene expression is controlled, at least in part, at the level of transcription. Immunofluorescence data ident ify the macroschizont as the location for both Tash2 I and Tash2 gene produ cts. Northern blot analysis of these genes indicated that their mRNA levels decrease during differentiation in vitro, at a time point coincident with major elevation in the mRNA levels of the merozoite antigen. Tams1, shown p reviously to be associated with commitment to merozoite production. Further more, experiments where cultures were incubated at 41 degreesC for 4 days a nd replaced at 37 degreesC for 2 days demonstrated that re-expression of Ta sh1 occurred and is probably linked to reversion to the macroschizont and d ecreased expression of Tams1. These results imply that the control of macro schizont and merozoite gene expression during differentiation is closely co -ordinated temporally. In addition, a comparison of Tash2 and Tams1 express ion has indicated that translational or post-translational control of gene expression may operate in the undifferentiated macroschizont. (C) 2001 Else vier Science B.V. All rights reserved.