title: Parasite killing in malaria non-vector mosquito Anopheles culicifacies species B: implication of nitric oxide synthase upregulation.
abstract: BACKGROUND
  Anopheles culicifacies, the main vector of human malaria in rural India, is a complex of five sibling species. Despite being phylogenetically related, a naturally selected subgroup species B of this sibling species complex is found to be a poor vector of malaria. We have attempted to understand the differences between vector and non-vector Anopheles culicifacies mosquitoes in terms of transcriptionally activated nitric oxide synthase (AcNOS) physiologies to elucidate the mechanism of refractoriness. Identification of the differences between genes and gene products that may impart refractory phenotype can facilitate development of novel malaria transmission blocking strategies.
  
  
  RESULTS
  We conducted a study on phylogenetically related susceptible (species A) and refractory (species B) sibling species of An. culicifacies mosquitoes to characterize biochemical and molecular differences in AcNOS gene and gene elements and their ability to inhibit oocyst growth. We demonstrate that in species B, AcNOS specific activity and nitrite/nitrates in mid-guts and haemolymph were higher as compared to species A after invasion of the mid-gut by P. vivax at the beginning and during the course of blood feeding. Semiquantitative RT-PCR and real time PCR data of AcNOS concluded that this gene is more abundantly expressed in midgut of species B than in species A and is transcriptionally upregulated post blood meals. Dietary feeding of L-NAME along with blood meals significantly inhibited midgut AcNOS activity leading to an increase in oocyst production in An. culicifacies species B.
  
  
  CONCLUSIONS
  We hypothesize that upregulation of mosquito innate cytotoxicity due to NOS in refractory strain to Plasmodium vivax infection may contribute to natural refractoriness in An. culicifacies mosquito population. This innate capacity of refractory mosquitoes could represent the ancestral function of the mosquito immune system against the parasite and could be utilized to understand the molecular basis of refractoriness in planning effective vector control strategies.
authors.affiliation: Protein Biochemistry and Structural Biology Laboratory, National Institute of Malaria Research (ICMR), Dwarka, New Delhi, India.
authors.forename: Sonam
authors.initials: S
authors.lastname: Vijay
authors.forename: Manmeet
authors.initials: M
authors.lastname: Rawat
authors.forename: Tridibes
authors.initials: T
authors.lastname: Adak
authors.forename: Rajnikant
authors.initials: R
authors.lastname: Dixit
authors.forename: Nutan
authors.initials: N
authors.lastname: Nanda
authors.forename: Harish
authors.initials: H
authors.lastname: Srivastava
authors.forename: Joginder K
authors.initials: JK
authors.lastname: Sharma
authors.forename: Godavarthi B K S
authors.initials: GB
authors.lastname: Prasad
authors.forename: Arun
authors.initials: A
authors.lastname: Sharma
mesh_terms: D000293:Adolescent; D000595:Amino Acid Sequence; D000818:Animals; D000852:Anopheles / Q000201:enzymology* / Q000235:genetics* / Q000276:immunology / Q000469:parasitology; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D006458:Hemolymph / Q000378:metabolism; D006801:Humans; D007113:Immunity, Innate / Q000235:genetics; D007303:Insect Vectors / Q000201:enzymology / Q000235:genetics / Q000276:immunology / Q000469:parasitology; D007422:Intestines / Q000201:enzymology / Q000276:immunology / Q000469:parasitology; D007700:Kinetics; D016780:Malaria, Vivax / Q000469:parasitology* / Q000635:transmission; D008969:Molecular Sequence Data; D009566:Nitrates / Q000097:blood; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009573:Nitrites / Q000097:blood; D033661:Oocysts / Q000254:growth & development; D010802:Phylogeny; D010966:Plasmodium vivax / Q000254:growth & development / Q000502:physiology*; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity; D015533:Transcriptional Activation; D015854:Up-Regulation
chemical_list: D009566:Nitrates; D009573:Nitrites; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase