From Perforin like Protein (PLP) annotation in Babesia bigemina to evolutionary history of MACPF-DOMAIN in Piroplasmida (Apicomplexa)

REGO N; PETRIGH R; NAYA H; FARBER M

New Orleans

Conferencia; 11th International Conference on Molecular Epidemiology and Evolutionary Genetics of Infectious Diseases,; 2012

Elsevier

Babesia bigemina and B. bovis are intraerythrocytic apicomplexans that causes babesiosis in cattle, a tick-transmitted disease worldwide distributed. Some of the steps involved in host cell-infection depend on secreted proteins. Studies in Plasmodium yoelii reported a secreted protein family containing membrane-attack complex/perforin (MACPF)-like domains known as Perforin Like Proteins (PLP). Aiming to understand PLPs importance for babesia transmission, we searched for plp gene repertoire in B. bigemina and studied the phylogenetic relationships with previously known apicomplexa PLPs. MACPF domains from annotated B. bovis PLPs were used to perform TBLASTN searches on B. bigemina contigs. FGENESH and Glimmer HMM trained with P. falciparum and B. bovis respectively, were used for annotation. Manual refinement of predictions was performed with Artemis. Due to the high divergence of apicomplexan PLPs, phylogenetic analysis was focused on the MACPF domains.  The alignment was assisted by a structural profile derived from the superimposition of known structures and phylogeny inferred trough Maximum Likelihood ptimization. Alternatively, a simultaneous Bayesian estimation of alignment and phylogeny was conducted (Bali-Phy). Eight coding sequences with MACPF domain were determined in B. bigemina partial assembly. In a novel arrangement, B. bovis is predicted to encode multiple MACPF domains (3) within a single protein. However, B. bigemina does not show this peculiar PLP structure. RT-PCR experiments revealed the expression of all plp genes in the B. bigemina vertebrate stage. Evolutionary history is complex in PLP family, as can be deduced from the inferred tree. Some duplication events preceded piroplasmids and haemosporidians divergence, while others are exclusive of each lineage. In a parsimony framework, we infer at least 4 PLPs present in the common ancestor of Piroplasmida and Haemosporida. The MACPF domain not only expand but also appear to have gathered at least twice independently in piroplasmids, leading to a gene structure with 3 domains in B. bovis and T. annulata.