title: The transcriptional response to encystation stimuli in Giardia lamblia is restricted to a small set of genes.
abstract: The protozoan parasite Giardia lamblia undergoes stage differentiation in the small intestine of the host to an environmentally resistant and infectious cyst. Encystation involves the secretion of an extracellular matrix comprised of cyst wall proteins (CWPs) and a β(1-3)-GalNAc homopolymer. Upon the induction of encystation, genes coding for CWPs are switched on, and mRNAs coding for a Myb transcription factor and enzymes involved in cyst wall glycan synthesis are upregulated. Encystation in vitro is triggered by several protocols, which call for changes in bile concentrations or availability of lipids, and elevated pH. However, the conditions for induction are not standardized and we predicted significant protocol-specific side effects. This makes reliable identification of encystation factors difficult. Here, we exploited the possibility of inducing encystation with two different protocols, which we show to be equally effective, for a comparative mRNA profile analysis. The standard encystation protocol induced a bipartite transcriptional response with surprisingly minor involvement of stress genes. A comparative analysis revealed a core set of only 18 encystation genes and showed that a majority of genes was indeed upregulated as a side effect of inducing conditions. We also established a Myb binding sequence as a signature motif in encystation promoters, suggesting coordinated regulation of these factors.
authors.affiliation: Institute of Parasitology, University of Zurich, Switzerland.
authors.forename: Laura
authors.initials: L
authors.lastname: Morf
authors.forename: Cornelia
authors.initials: C
authors.lastname: Spycher
authors.forename: Hubert
authors.initials: H
authors.lastname: Rehrauer
authors.forename: Catharine Aquino
authors.initials: CA
authors.lastname: Fournier
authors.forename: Hilary G
authors.initials: HG
authors.lastname: Morrison
authors.forename: Adrian B
authors.initials: AB
authors.lastname: Hehl
mesh_terms: D000818:Animals; D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D016829:Giardia lamblia / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism
chemical_list: C094333:CWP1 protein, Giardia lamblia; C470735:Myb2 protein, Giardia lamblia; D015800:Protozoan Proteins; D015534:Trans-Activators