Phylogenomic Analysis of the α Proteasome Gene Family from Early-Diverging Eukaryotes

We employed a phylogenomic approach to study the evolution of α subunits of the proteasome gene family from early diverging eukaryotes. BLAST similarity searches of the Giardia lamblia genome identified all seven α proteasome genes characteristic of eukaryotes from the crown group. In addition, a PCR strategy for the amplification of multiple α subunit sequences generated single α proteasome products for representatives of the Kinetoplastida (Leishmania major), the Parabasalia (Trichomonas vaginalis), and the Microsporidia (Vairimorpha sp., Nosema sp., Endoreticulata sp., and Spraguea lophii). The kinetoplastid Trypanosoma cruzi and the eukaryote crown group Acanthamoeba castellanii yielded two distinct α proteasome genes each. The presence of seven distinct α proteasome genes in G. lamblia, one of the earliest-diverging eukaryotes, indicates that the α proteasome gene family evolved rapidly from a minimum of one gene in Archaea to seven or more in Eukarya. Results from the phylogenomic analysis are consistent with the idea that the Diplomonida (as represented by G. lamblia), the Kinetoplastida, the Parabasalia, and the Microsporidia diverged after the duplication events that originated the α proteasome gene family. A model for the early origin and evolution of the proteasome gene family is presented. Received: 14 February 2000 / Accepted: 14 August 2000     

An Endoreticulatus species from Ocinara lida (Lepidoptera: Bombycidae) in Taiwan

A microsporidium from the Ficus pest, Ocinara lida, in Taiwan is characterized. The taxonomic position of this species was preliminarily determined by sequencing small subunit rRNA gene (SSUrRNA). Analysis of the SSUrRNA sequence indicated that this isolate from O. lida is a member of the genus Endoreticulatus and belongs to the genetic grouping containing other lepidopteran Endoreticulatus species we have analyzed phylogenetically. The taxonomic position of this isolate was also confirmed by the ultrastructural characteristics of this isolate. The congruence between SSUrRNA sequence analysis and ultrastructural characteristics shows that this isolate is more closely related to Endoreticulatus bombycis than to Endoreticulatus schubergi Zw?lfer.     

Survey of bumble bee (Bombus) pathogens and parasites in Illinois and selected areas of northern California and southern Oregon

Pathogens have been implicated as potential factors in the recent decline of some North American bumble bee (Bombus) species, but little information has been reported about the natural enemy complex of bumble bees in the United States. We targeted bumble bee populations in a state-wide survey in Illinois and several sites in California and Oregon where declines have been reported to determine presence and prevalence of natural enemies. Based on our observations, most parasites and pathogens appear to be widespread generalists among bumble bee species, but susceptibility to some natural enemies appeared to vary.     

Effect of entomopathogenic nematodes on Plectrodera scalator (Fabricius) (Coleoptera: Cerambycidae)

Entomopathogenic nematodes were screened for efficacy against the cottonwood borer, Plectrodera scalator (Fabricius). Steinernema feltiae SN and S. carpocapsae All killed 58 and 50% of larvae, respectively, in filter paper bioassays but less than 10% in diet cup bioassays. S. glaseri NJ, S. riobrave TX, and H. indica MG-13 killed less than 10% of larvae in both assays. H. marelata IN was ineffective in the diet cup bioassay and killed 12.9% of larvae in a filter paper bioassay. The nematode isolates we tested are not suitable for use as biological control agents against P. scalator.     

Transmission as a predictor of ecological host specificity with a focus on vertical transmission of microsporidia

Consideration of vertical transmission is particularly important for understanding the life cycles of entomopathogens that are naturally occurring in invertebrate populations, are a problem in beneficial insect colonies, or are under consideration as classical biological control agents. Empirical studies generally corroborate the evolutionary hypothesis that virulence should be relatively low for pathogen species that utilize vertical transmission as one mechanism for maintenance in the host population. Nevertheless, many entomopathogens with significant effects on host populations are vertically as well as horizontally transmitted. In addition to gaining a better understanding of pathogen-host interactions and population dynamics, studies of the host range and specificity of putative biological control agents can benefit by using transmission studies to better predict ecological host specificity from physiological data. Horizontal transmission requires a tightly organized host-pathogen relationship to succeed, but still involves, albeit restricted by host behavior and pathogen dosage, the physiological susceptibility of the nontarget host. Vertical transmission studies can provide increased stringency for determining the ecological host specificity of a species and may be one very accurate predictor of the ability of a pathogen to successfully host-switch when introduced into a na?ve population.     

Immunohistochemical localization of the early embryonic antigen (SSEA-1) in postimplantation mouse embryos and fetal and adult tissues

Distribution of the stage-specific embryonic antigen (SSEA-1) was studied in postimplantation murine embryos, fetuses, and adult mice by immunohistochemical techniques. SSEA-1 was also localized on the stem cells of differentiating solid teratocarcinomas and on the surface of core cells of solid embryoid bodies. At the egg cylinder stage the antigen is restricted to embryonic ectoderm and visceral endoderm. During subsequent development SSEA-1 becomes localized to portions of the brain and primordial germ cells. In addition some sites of the urogenital anlage are SSEA-1 positive. In adult mice, the epithelium of the oviduct, the endometrium, and the epididymis are the cells most reactive with the monoclonal antibody to SSEA-1; although some areas of the brain and kidney tubules are weakly positive. Study of this antigenic determinant might disclose some previously unexpected cell lineage relationships and/or might elucidate events necessary for reproduction.     

Hemolymph melanization and alterations in hemocyte numbers in Lymantria dispar larvae following infections with different entomopathogenic microsporidia

Lymantria dispar (L.) (Lepidoptera: Lymantriidae) larvae can be infected in the laboratory with a variety of entomopathogenic microsporidia. In many cases, however, L. dispar is only a semi‐permissive host for such infections. In this study, we analyzed changes in the melanization of hemolymph and hemocyte numbers in L. dispar larvae after inoculation with various entomopathogenic microsporidia. We compared the infections produced by microsporidia isolated from L. dispar and infections produced by isolates from other Lepidoptera to which L. dispar is only a semi‐permissive host. Microsporidiosis induced a significant activation of the prophenoloxidase system leading to melanization; activation was highest when the pathogen caused heavy infections of the fat body, which was the case with two microsporidia originally isolated from L. dispar. Infection of only the silk glands or light infection of the fat body by two Vairimorpha spp. from other lepidopteran hosts elicited a lower response. Very light infections caused by a microsporidium isolated from Malacosoma americanum were not accompanied by elevated hemolymph melanization activity. Heavy infections by Endoreticulatus spec. that remained restricted to the gut tissue likewise did not elicit melanization. One Vairimorpha spec. from L. dispar induced a significant increase in total hemocyte numbers; the other infections led to temporarily decreased numbers. Microscopic examinations showed that parts of infected tissue were encapsulated by hemocytes. We conclude that measured alterations in hemolymph melanization and hemocyte numbers were likely to be induced by the damaging effects of heavy infections. Observed defense responses did not prevent the progression of infections.     

Teratocarcinogenesis as related to the age of embryos grafted under the kidney capsule

Summary Mouse egg-cylinders of C3H/H strain with two and three germ layers were transplanted under the kidney capsule. They developed into well differentiated teratomas and teratocarcinomas. Older embryos developed invariably into teratomas composed of adult tissues only. We consider the period of germ layer inversion as a critical stage when embryonic cells loose their potentiality for uncontrolled growth.     

Reprogramming is essential in nuclear transfer

Fertile offspring have been produced by nuclear transfer from adult somatic cells in several mammalian species (Wilmut et al., 1997; Kato et al., 1998; Wakayama et al., 1998; Polejaeva et al., 2000; Chesne et al., 2002; Shin et al., 2002; Zhou et al., 2003). Various possible causes have been suggested for the overall low efficiency (Perry and Wakayama, 2002). Notably, however, it has not yet been clearly demonstrated whether reprogramming after nuclear transfer is necessary for successful cloning. Here we show that reprogramming is essential in nuclear transfer, by comparing the developmental efficiency after the transfer of cumulus cell nuclei with that for zygote nuclei. Nuclear transfers from blastomeres of a series of pre-implantation stages showed further that, as development proceeds, the nuclei progressively lose their potency and become more difficult to reprogram upon their transfer into enucleated MII oocytes. We also found that naturally ovulated oocytes are much better recipients of a nucleus than are superovulated oocytes, which have been used in all the nuclear transfer experiments reported so far. This indicates that cloning efficiency can also be increased to some extent by technical improvements. All these results enable us to distinguish more clearly between the inherent problem of reprogramming and technical problems associated with materials, manipulation, and in vitro culture.     

Physiological host specificity: a model using the European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) and microsporidia of row crop and other stalk-boring hosts

We investigated vertical and horizontal transmission as means by which entomopathogenic microsporidia may be isolated in their hosts. Ostrinia nubilalis larvae were challenged with microsporidia isolated from other stalk-boring and row crop Lepidoptera and were susceptible to seven species. Two species were horizontally transmitted. A Nosema sp. from Eoreuma loftini was transmitted among O. nubilalis larvae but not among larvae of the E. loftini host. This species was also vertically transmitted to the offspring of infected O. nubilalis females. An rDNA sequence showed the E. loftini isolate to be Nosema pyrausta, a naturally occurring species in O. nubilalis. Our results suggest that both horizontal and vertical transmission provide physiological barriers to host switching in the microsporidia, thus restricting the natural host range.