Reduction of testis growth of pseudaletia separata larvae after parasitization by cotesia kariyai

Abstract

The braconid endoparasitoid, Cotesia j=Apante/es) kariyai physiologically influences its host, Pseudaletia separata, through three factors: polydnavirus, venom, and teratocytes. Inhibiting testis development of the host seems to be one factor that is important for successful development of the parasitoid. CkPV (polydnavirus of Cotesia kariyai) plus venom depressed testis development. Testes from unparasitized day 0 last instar transplanted into isolated abdomens increased in volume after stimulation with 20-hydroxyecdysone (20HE). However, day 0 testis preincubated with CkPV plus venom for 6 h and then transplanted into an isolated abdomen did not respond to 20HE. Southern blot analysis indicated CkPV-DNA hybridized to testes-DNA from parasitized hosts, suggesting the possibility that CkPV is involved in suppression of testes growth. Binding assays using PNA indicated a 2-fold increase in ecdysteroid receptor binding activity during the late stage of parasitism. The increase in receptor activity might be related to the maintenance of a low ecdysteroid titer in parasitized hosts due to a feedback response. 0 1994 Wiley-Liss, Inc. Key words: braconid parasitoid, polydnavirus, venom, ecdysone receptor INTRODUCTIONEndoparasitoids often affect the physiological condition and behavior of their hosts [l]. Parasitism of Pseudaletia sepavata (Walker) by Cotesia (=Apanteles) kariyai (Watanabe) caused several physiological alterations, including inhibition of host pupation [2,31, changes in fat body metabolism [41, and disruption of the immune system [5,6]. Host behavior is also changed during parasitism.

Parasitic castration of Plutella xylostella larvae induced by polydnaviruses and venom of Cotesia vestalis and Diadegma semiclausum

“…In the C. congregata -M. sexta system, the amount of CcBV and venom exceeded the physiological dosages needed to elicit behavioral and developmental alternations but were still incapable of mimicking the marked testicular atrophy found in naturally parasitized hosts . In sharp contrast, as little as one-third of a wasp equivalent of CkBV was sufficient to mimic the effect on the testes seen in naturally parasitized larvae in the C. kariyai-P. separate system (Yagi and Tanaka, 1992;Tanaka et al, 1994). In comparison with these results, the physiological dosages of CvBV plus venom caused severe parasitic castration in P. xylostella larvae in the absence of developing parasitoid larva.…”

“…The number of developing germ cells is reduced and the structural integrity of the testis sheath is compromised . After injection of CkBV plus venom into Pseudoletia separata, abnormal chromosomes in specific germ cells were observed and mimicked the effects of natural parasitization on the testes (Tanaka et al, 1994). These results suggested the possibility that specific stages of the germ cells might be affected by CkBV plus venom (Tagashira and Tanaka, 1998).…”

Related RNAs in Lepidopteran Cells after in Vitro Infection with Hyposoter didymator Virus Define a New Polydnavirus Gene Family

“…Indeed, parasitic wasps evade some immune responses of the host insect larvae through expression of PDV genes (Asgari et al, 1996(Asgari et al, ,1997Lavine and Beckage, 1995;Shelby et al, 1998;Strand et al, 1997;Yamanaka et al, 1996). In addition, expression of PDV genes causes some cellular and physiological effects in the parasitized host, among them hormonal and development changes (Beckage et al, 1994;Lawrence and Lanzrein, 1993;Tanaka et al, 1994). Regarding infection, several tissues of the lepidopteran host are known to be infected.…”

Venom proteins from polydnavirus‐producing endoparasitoids: Their role in host‐parasite interactions

“…In Heliothis virescens (Noctuidae), both venom and calyx fluids from the parasitoid Cardiochiles nigriceps (Braconidae) are required for inhibition of prothoracic gland activity (Tanaka and Vinson, 1991a). Venom and C. kariyai PDVs together cause reduction of testis growth of P. separata larvae (Tanaka et al, 1994) and inhibition of host pupation (Tanaka and Vinson, 1991b). Neither alone was able to cause similar effects.…”