Abstract:  Vitellogenin (Vg) is the major yolk protein precursor which is synthesized abundantly in the insect fat body after the female ingests blood meal. The regulatory elements of vitellogenin have been used to drive the tissue specific expression of anti parasitic gene in mosquitoes, where its maximum interaction could take place with the parasite. However, no endogenous promoter has been analysed so far in the Indian malaria vector Anopheles culicifacies which is responsible for 60%-70% of malaria cases in India. In this study, the vitellogenin gene including 5′ upstream regulatory region of Anopheles culicifacies was cloned after PCR amplification and named AncuVg (GenBank accession number JN113091). It contains an ORF of approximately 6.2 kb encoding 2 052 amino acids with a putative signal peptide of 16 residues. It also contains an N_Vitellogenin region and a VWF type D domain, that are found conserved in other insect Vgs too. The molecular weight of the predicted polypeptide is 238.0 kDa. It possesses four consensus (RXXR/S) cleavage sites and close to the C-terminus there is a GL/ICG motif followed by nine cysteine residues and a DGXR motif, located 18 residues upstream from the GL/ICCG motif. Three polyserine regions were found in the deduced amino acid sequence: two in the amino terminal region and one in the carboxy terminal region. The extent of codon bias in mosquito vitellogenin genes based on the relative synonymous codon usage values were determined by the effective number of codons. The 3D structure of A. culicifacies Vg was also predicted. The 5′ upstream region of the AncuVg gene was analyzed to understand the regulation of Vg gene transcription. Phylogenetic analysis using the 5′ upstream region of Vg genes showed their conformation to three major clades among mosquitoes. Homology and other characteristic features of Vg have also been analyzed using various bioinformatic tools.

Key words: Anopheles culicifacies, vitellogenin, mosquito, phylogenetic analysis, polyserine, transcription factor