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Analysis of blood-induced Anopheles gambiae midgut proteins and sexual stage Plasmodium falciparum interaction reveals mosquito genes important for malaria transmission.

ABSTRACT: Plasmodium invasion of mosquito midguts is a mandatory step for malaria transmission. The roles of mosquito midgut proteins and parasite interaction during malaria transmission are not clear. This study aims to identify mosquito midgut proteins that interact with and affect P. falciparum invasion. Based on gene expression profiles and protein sequences, 76 mosquito secretory proteins that are highly expressed in midguts and up-regulated by blood meals were chosen for analysis. About 61 candidate genes were successfully cloned from Anopheles gambiae and expressed in insect cells. ELISA analysis showed that 25 of the insect cell-expressed recombinant mosquito proteins interacted with the P. falciparum-infected cell lysates. Indirect immunofluorescence assays confirmed 17 of them interacted with sexual stage parasites significantly stronger than asexual stage parasites. Knockdown assays found that seven candidate genes significantly changed mosquitoes' susceptibility to P. falciparum. Four of them (AGAP006268, AGAP002848, AGAP006972, and AGAP002851) played a protective function against parasite invasion, and the other three (AGAP008138, FREP1, and HPX15) facilitated P. falciparum transmission to mosquitoes. Notably, AGAP008138 is a unique gene that only exists in Anopheline mosquitoes. These gene products are ideal targets to block malaria transmission.

SUBMITTER: Cui Y

PROVIDER: S-EPMC7459308 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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Analysis of blood-induced Anopheles gambiae midgut proteins and sexual stage Plasmodium falciparum interaction reveals mosquito genes important for malaria transmission.

Cui Yingjun Y Niu Guodong G Li Vincent L VL Wang Xiaohong X Li Jun J

Scientific reports 20200831 1

Plasmodium invasion of mosquito midguts is a mandatory step for malaria transmission. The roles of mosquito midgut proteins and parasite interaction during malaria transmission are not clear. This study aims to identify mosquito midgut proteins that interact with and affect P. falciparum invasion. Based on gene expression profiles and protein sequences, 76 mosquito secretory proteins that are highly expressed in midguts and up-regulated by blood meals were chosen for analysis. About 61 candidate ...[more]

PMID: 32868841

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Project description:BackgroundMalaria is caused by Plasmodium parasites, which are transmitted via the bites of infected Anopheline mosquitoes. Midgut invasion is a major bottleneck for Plasmodium development inside the mosquito vectors. Malaria parasites in the midgut are surrounded by a hostile environment rich in digestive enzymes, while a rapidly responding immune system recognizes Plasmodium ookinetes and recruits killing factors from the midgut and surrounding tissues, dramatically reducing the population of invading ookinetes before they can successfully traverse the midgut epithelium. Understanding molecular details of the parasite-vector interactions requires precise measurement of nascent protein synthesis in the mosquito during Plasmodium infection. Current expression profiling primarily monitors alterations in steady-state levels of mRNA, but does not address the equally critical issue of whether the proteins encoded by the mRNAs are actually synthesized.ResultsIn this study, we used sucrose density gradient centrifugation to isolate actively translating Anopheles gambiae mRNAs based upon their association with polyribosomes (polysomes). The proportion of individual gene transcripts associated with polysomes, which is determined by RNA deep sequencing, reflects mRNA translational status. This approach led to identification of 1017 mosquito transcripts that were primarily regulated at the translational level after ingestion of Plasmodium falciparum-infected blood. Caspar, a negative regulator of the NF-kappaB transcription factor Rel2, appears to be substantially activated at the translational levels during Plasmodium infection. In addition, transcripts of Dcr1, Dcr2 and Drosha, which are involved in small RNA biosynthesis, exhibited enhanced associations with polysomes after P. falciparum challenge. This observation suggests that mosquito microRNAs may play an important role in reactions against Plasmodium invasion.ConclusionsWe analyzed both total cellular mRNAs and mRNAs that are associated with polysomes to simultaneously monitor transcriptomes and nascent protein synthesis in the mosquito. This approach provides more accurate information regarding the rate of protein synthesis, and identifies some mosquito factors that might have gone unrecognized because expression of these proteins is regulated mainly at the translational level rather than at the transcriptional level after mosquitoes ingest a Plasmodium-infected blood meal.

Project description:Malaria is caused by Plasmodium parasites, which are transmitted via the bites of infected Anopheline mosquitoes. Midgut invasion is a major bottleneck for Plasmodium development inside the mosquito vectors as a rapidly responding immune system recognizes ookinetes and recruits killing factors from the midgut and surrounding tissues, dramatically reducing the population of invading ookinetes before they can successfully traverse the midgut epithelium. Understanding molecular details of the parasite-vector interactions requires precise measurement of nascent protein synthesis in the mosquito during Plasmodium infection. Current expression profiling primarily monitors alterations in steady-state levels of mRNA, but does not address the equally critical issue of whether the proteins encoded by the mRNAs are actually synthesized. In this study, we used sucrose density gradient centrifugation to isolate actively translating Anopheles gambiae mRNAs based upon their association with polyribosomes (polysomes). The proportion of individual gene transcripts associated with polysomes, which is determined by RNA deep sequencing, reflects mRNA translational status. This approach led to identification of 1017 mosquito transcripts that were primarily regulated at the translational level after ingestion of Plasmodium falciparum-infected blood. Caspar, a negative regulator of the NF-kappaB transcription factor Rel2, appears to be substantially activated at the translational levels during Plasmodium infection. In addition, transcripts of Dcr1, Dcr2 and Drosha, which are involved in small RNA biosynthesis, exhibited enhanced associations with polysomes after P. falciparum challenge. This observation suggests that mosquito microRNAs may play an important role in reactions against Plasmodium invasion. We analyzed both total cellular mRNAs and mRNAs that are associated with polysomes to simultaneously monitor transcriptomes and nascent protein synthesis in the mosquito. This approach provides more accurate information regarding the rate of protein synthesis, and identifies some mosquito factors that might have gone unrecognized because expression of these proteins is regulated mainly at the translational level rather than at the transcriptional level after mosquitoes ingest a Plasmodium-infected blood meal.

Project description:Genome sequencing of Anopheles gambiae was completed more than ten years ago and has accelerated research on malaria transmission. However, annotation needs to be refined and verified experimentally, as most predicted transcripts have been identified by comparative analysis with genomes from other species. The mosquito midgut-the first organ to interact with Plasmodium parasites-mounts effective antiplasmodial responses that limit parasite survival and disease transmission. High-throughput Illumina sequencing of the midgut transcriptome was used to identify new genes and transcripts, contributing to the refinement of An. gambiae genome annotation.We sequenced ~223 million reads from An. gambiae midgut cDNA libraries generated from susceptible (G3) and refractory (L35) mosquito strains. Mosquitoes were infected with either Plasmodium berghei or Plasmodium falciparum, and midguts were collected after the first or second Plasmodium infection. In total, 22,889 unique midgut transcript models were generated from both An. gambiae strain sequences combined, and 76% are potentially novel. Of these novel transcripts, 49.5% aligned with annotated genes and appear to be isoforms or pre-mRNAs of reference transcripts, while 50.5% mapped to regions between annotated genes and represent novel intergenic transcripts (NITs). Predicted models were validated for midgut expression using qRT-PCR and microarray analysis, and novel isoforms were confirmed by sequencing predicted intron-exon boundaries. Coding potential analysis revealed that 43% of total midgut transcripts appear to be long non-coding RNA (lncRNA), and functional annotation of NITs showed that 68% had no homology to current databases from other species. Reads were also analyzed using de novo assembly and predicted transcripts compared with genome mapping-based models. Finally, variant analysis of G3 and L35 midgut transcripts detected 160,742 variants with respect to the An. gambiae PEST genome, and 74% were new variants. Intergenic transcripts had a higher frequency of variation compared with non-intergenic transcripts.This in-depth Illumina sequencing and assembly of the An. gambiae midgut transcriptome doubled the number of known transcripts and tripled the number of variants known in this mosquito species. It also revealed existence of a large number of lncRNA and opens new possibilities for investigating the biological function of many newly discovered transcripts.

Dataset Information

Analysis of blood-induced Anopheles gambiae midgut proteins and sexual stage Plasmodium falciparum interaction reveals mosquito genes important for malaria transmission.

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Analysis of blood-induced Anopheles gambiae midgut proteins and sexual stage Plasmodium falciparum interaction reveals mosquito genes important for malaria transmission.

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