VAP applied to mVSG expression in experimentally infected tsetse mouthparts. (A) Transcriptomic VAPs of trypanosomes extracted from tsetse mouthparts. VAPs from the transcriptomes are remarkably similar yet significantly different from the genomic VSG repertoire (Poisson regression, P < 0.001) and the VSG found at telomeric expression sites. Infection 1 represents a sample of 40 pooled mouthparts; infection 2 represents 24 individual mouthparts; infection 3 represents a sample of 131 pooled mouthparts after metacyclic parasite enrichment by anion exchange chromatography. The genomic VAP represents the average profile of 24 sets of 79 VSGs randomly sampled from the genome of Tc1/148. Stacked columns are color-coded by phylotype according to the key. The number of VSG transcripts recovered in each sample infection is noted in the figure. (B) Comparison of average phylotype proportion (adjusted for transcript abundance) in transcriptomic samples presented in A and genomic profiles from a random selection of VSG of Tc1/148 (mean ± σ). Statistical analysis reveals that, in comparison to the genome, P7, P12, and P15 are underrepresented in the transcriptomes (independent t-test, P-value <0.001), while P4, P8, P9, and P11 are significantly overrepresented (independent t-test, P-value <0.001). (C) ML phylogeny of P8 showing 12 distinct loci found across our T. congolense strain genomes (denoted by gray boxes), the position of Tc1/148 P8 transcripts, and those from two previous studies (Eshita et al. [1992] [UniProt ID “M74803.1” and “M74802.1”] and Helm et al. [2009] [“mVSG1”]). Internal nodes are labeled with bootstrap values greater than 70.
