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Polydnaviruses of Braconid Wasps Derive from an Ancestral Nudivirus

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Science  13 Feb 2009:
Vol. 323, Issue 5916, pp. 926-930
DOI: 10.1126/science.1166788

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  1. Fig. 1.

    Organization of nudivirus-related genes in the wasp genome (Cotesia congregata). Five genes (38K, HzNVorf9-like1, HzNVorf89-like, pif-3, and PmV-like) are organized as a cluster that is likely to constitute a remnant of the virus integrated into the ancestral wasp genome. Two genes (HzNVorf128-like and lef-8) are located within the same 60-kb chromosomal region; other genes (odv-e56-1, p74, and HzNVorf140-like) are dispersed and located in regions containing Cotesia congregata putative homologs of insect genes (in blue) and/or remnants of mobile elements (in gray). For nudivirus-related genes, the presence of sequences found in promoters of baculovirus genes transcribed by the cellular RNA polymerase (E) or baculovirus RNA polymerase (L) is indicated (19). E indicates the presence of a TATAA sequence with a CA(T/G)T or a CGTGC transcription start site 20 to 40 nucleotides downstream. L indicates the presence of a (A/T/G)TAAG motif within 300 nucleotides upstream of the translation start codon. CDS, coding sequence; ORF, open reading frame. Acyrthosiphon pisum (pea aphid), Drosophila ananassae (fruit fly), and Nasonia vitripennis (parasitoid wasp).

  2. Fig. 2.

    Nudivirus-related gene expression correlates temporally with bracovirus particle production and occurs in the same tissue. (A) Real-time RT-PCR indicates that three nudivirus-related genes(HzNVorf89-like coding for a structural component of CcBV particles, p74, and odv-e56-1) are induced in female pupae from day 4, coincident with the initiation of particle production as detected by transmission electron microscopy (TEM) and PCR (26). The induction of p47, coding for one of the viral RNA polymerase subunits, occurs earlier, which would be expected if the viral RNA polymerase controls the expression of some nudivirus-related genes. Although baculovirus regulatory sequences are present in some promoters (see Fig. 1), they appear to be too short and, therefore, would lack the specificity necessary to selectively express chromosomally integrated genes. The four nudivirus-related genes are specifically expressed in the calyx region of the ovaries where bracovirus particles are produced, but not in the oviducts (B) nor in males (A). Asterisk indicates expression too low to be indicated. On wasp ovaries: o, oviduct; c, calyx.

  3. Fig. 3.

    Conservation of the machinery producing bracovirus particles among microgastroid wasps. The tree and dates of radiations are taken from (25). (A) Nudivirus-related genes amplified with DNA from species belonging to different subfamilies: C. congregata (Microgastrinae), Toxoneuron nigriceps (Cardiochilinae), Mirax sp. (Miracinae), Epsilogaster sp. (Mendesellinae), Sania sp. (Khoikhoiinae), and C. inanitus (Cheloninae). (B) Alignment of HzNVORF9-like1 and HzNVORF128-like proteins deduced from the amplified sequences. (C) Bracovirus particles visualized by TEM from C. congregata, Mirax sp., and C. inanitus. n, Nucleocapsid. The particles contain one (CiBV) or several nucleocapsids (CcBV and MspBV), dispersed (CcBV) or organized (MspBV).

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