Polydnavirus of the parasitic wasp Chelonus inanitus (Braconidae): characterization, genome organization and time point of replication

Abstract

HindlII and 23 EcoRI clones were obtained. Southern blots revealed that complete and unrearranged segments were cloned with this approach, and restriction maps for five segments were obtained. Part of a 16.8 kbp segment was sequenced, found to be AT-rich (73%) and to contain six copies of a 17 bp repeated sequence. The development of the female reproductive tract in the course of pupal-adult development of the wasp was investigated and seen to be strictly correlated with the pigmentation pattern. By the use of a semiquantitative PCR, replication of viral DNA was observed to initiate at a specific stage of pupal-adult development.

Ovary development and polydnavirus morphogenesis in the parasitic wasp Chelonus inanitus. I. Ovary morphogenesis, amplification of viral DNA and ecdysteroid titres

“…Proviral CiV segments appear to be clustered in the genome of the wasp, as flanking regions of CiV12 and CiV14 have been shown to hybridize to other viral segments (Wyder et al, 2002). The morphogenesis of the ovary in the course of pupal-adult development is strictly correlated with the pigmentation pattern of the pupae and has been subdivided into stages 1-6 (Albrecht et al, 1994). Excision and circularization of viral DNA has been shown to commence at stage 3b (Gruber et al, 1996;Wyder et al, 2002).…”

“…In (c) the calyx region is shown at higher magnification. Designation of pupal stages is according to Albrecht et al (1994). All pictures show one half of an ovary with the oviduct oriented to the left.…”

“…Details of the biology and rearing of parasitoid and host are given in Grossniklaus-Bürgin et al (1994). Assignment of stages in pupal-adult development was as described by Albrecht et al (1994).…”

“…The initiation of virus replication has been shown to be associated with a specific phase in pupal-adult development in the ichneumonid Campoletis sonorensis (Norton & Vinson, 1983) and the two braconids Chelonus inanitus and Cotesia congregata (Albrecht et al, 1994;Gruber et al, 1996;Savary et al, 1999;Pasquier-Barre et al, 2002). In C. sonorensis it has been proposed, on the basis of ligation and in vitro application of 20-hydroxyecdysone (20E), that this hormone may regulate polydnavirus replication (Webb & Summers, 1992).…”

Functional endogenous viral elements in the genome of the parasitoid wasp Cotesia congregata : insights into the evolutionary dynamics of bracoviruses

“…Strikingly, segments separated by small spacers (less than 500 bp) were in opposite orientation (13 of 16) except for those involved in nesting (see electronic supplementary material, table S4). As each nucleocapsid contains only one circle [36,37], this might reflect the physical constraints imposed during encapsidation for incorporating the DNA of adjacent segments into different nucleocapsids.…”