Abstract
The life cycle of the trypanosomatid Crithidia fasciculata is monogenetic, as the unique hosts of these parasites are different species of culicids. The comparison of these non-pathogenic microorganisms evolutionary close to other species of trypanosomatids that develop digenetic life cycles and cause chronic severe sickness to millions of people worldwide is of outstanding interest. A ground-breaking analysis of differential protein abundance in Crithidia fasciculata is reported herein. The comparison of the outcome with previous gene expression profiling studies developed in the related human pathogens of the genus Leishmania has revealed substantial differences between the motile stages of these closely related organisms in abundance of proteins involved in catabolism, redox homeostasis, intracellular signalling, and gene expression regulation. As L. major and L. infantum agglutinate with peanut lectin and non-agglutinating parasites are more infective, the agglutination properties were evaluated in C. fasciculata. The result is that choanomastigotes are able to agglutinate with peanut lectin and a non-agglutinating subpopulation can be also isolated. As a difference with L. infantum, the non-agglutinating subpopulation over-expresses the whole machinery for maintenance of redox homeostasis and the translation factors eIF5a, EF1α and EF2, what suggests a relationship between the lack of agglutination and a differentiation process.
Highlights
Protists of the genus Crithidia (Leger, 1902) (Kinetoplastida: Trypanosomatidae) are flagellate parasites that exclusively infect insects [1]
All proteins could be identified when MASCOT searches were performed against the reference genome sequence of C. fasciculata (Tables 1–3) when there was sufficient amount for identification, whereas a total of 20 constantly expressed proteins (Table S2 in S1 File), 41 differentially expressed proteins in the growth curve (Table S1 in S1 File) and 30 proteins with different abundance between PNA+ and PNA- choanomastigotes (Table S3 in S1 File) could be identified against the NCBInr database, which is 53.4% of the proteins analyzed by MALDI-TOF/TOF mass spectometry
Most of the identifications (73.9%) were consistent between the two databases and most of those successfully performed with the NCBInr database (63.9%) had the highest MASCOT scores for orthologue proteins of the genus Leishmania, whereas only 9.3% of them matched with a Trypanosoma spp. orthologue (Tables S1–S3 in S1 File)
Summary
Protists of the genus Crithidia (Leger, 1902) (Kinetoplastida: Trypanosomatidae) are flagellate parasites that exclusively infect insects [1]. C. fasciculata successfully infects many species of mosquitoes. These parasites are polymorphic, two stages are clearly distinguished. Amastigotes are non-motile round cells with a flagellum nonemergent from the cellular body. They are morphologically similar to amastigotes of the genus Leishmania, they are extracellular (reviewed in [2]). The life cycle of C. fasciculata is developed in the gut of the culicid, which becomes infected by ingestion of amastigotes voided with feces of other hosts. Choanomastigotes differentiate back into non-motile round amastigotes that are attached to the gut epithelium by hemidesmosomes [3] frequently leading to damage [4]. The larval and pupal instars of mosquitoes get infected in the aquatic habitat and amastigotes are transmitted to the adult mosquito through the metamorphosing gut [2] leading to completion of the life cycle (Fig. 1A)
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