Survival of Trypanosoma brucei in the tsetse fly is enhanced by the expression of specific forms of procyclin.
African trypanosomes are not passively transmitted, but they undergo several rounds of differentiation and proliferation within their intermediate host, the tsetse fly. At each stage, the survival and successful replication of the parasites improve their chances of continuing the life cycle, but little is known about specific molecules that contribute to these processes. Procyclins are the major surface glycoproteins of the insect forms of Trypanosoma brucei. Six genes encode proteins with extensive glutamic acid-proline dipeptide repeats (EP in the single-letter amino acid code), and two genes encode proteins with an internal pentapeptide repeat (GPEET). To study the function of procyclins, we have generated mutants that have no EP genes and only one copy of GPEET. This last gene could not be replaced by EP procyclins, and could only be deleted once a second GPEET copy was introduced into another locus. The EP knockouts are morphologically indistinguishable from the parental strain, but their ability to establish a heavy infection in the insect midgut is severely compromised; this phenotype can be reversed by the reintroduction of a single, highly expressed EP gene. These results suggest that the two types of procyclin have different roles, and that the EP form, while not required in culture, is important for survival in the fly.
Ruepp
S
S
Institut für Allgemeine Mikrobiologie, Universität Bern, CH-3012 Bern, Switzerland.
Furger
A
A
Kurath
U
U
Renggli
C K
CK
Hemphill
A
A
Brun
R
R
Roditi
I
I
D000595:Amino Acid Sequence; D000818:Animals; D004064:Digestive System / Q000469:parasitology; D017353:Gene Deletion; D018628:Gene Dosage; D015870:Gene Expression; D017125:Genes, Protozoan; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D011995:Recombination, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D014346:Trypanosoma brucei brucei / Q000254:growth & development / Q000378:metabolism*; D014370:Tsetse Flies / Q000469:parasitology*
D008562:Membrane Glycoproteins; D015800:Protozoan Proteins; C053277:procyclic acidic repetitive protein, Trypanosoma