Effects of the vertical distribution of a root-feeding insect (Anomala cuprea) on the yield, mortality, and size structure of Lolium perenne populations at different plant densities

The vertical distribution of belowground herbivores plays an important role in determining the performance of an individual plant, but we still do not know the effects of this distribution on plant populations. A grass (Lolium perenne L.) was, therefore, grown at two densities with three vertical distributions of the belowground herbivore Anomala cuprea Hope (Coleoptera: Scarabaeidae). The population yield decreased significantly in the treatments with a herbivore, and decreased most when the herbivore was in the top feeding zone (i.e., the shallowest soil). Plants only died when the herbivore was in the top zone or was free to move within the pot. At low plant density, the biomass of the three largest shoots decreased significantly in the presence of a herbivore, but that of shoots in the fourth and smaller ranks did not. At high plant density, shoot biomass was not significantly affected by herbivory, irrespective of plant size. The standard deviation of shoot size was larger at low densities than at high densities. At low, but not high plant densities, the standard deviation decreased when herbivory occurred in the shallowest soil layer. To our knowledge, this study is the first to demonstrate that the vertical distribution of a belowground herbivore can markedly affect the size dynamics of a plant population.

Effects of belowground herbivory on the survival and biomass of Lolium perenne and Plantago lanceolata plants at various growth stages

We examined the effects of a root-feeding beetle larva (Anomala cuprea Hope) on the survival and biomass of Lolium perenne L. and Plantago lanceolata L. plants at various ages. We hypothesized that belowground herbivory would kill more juveniles than mature plants because of greater root damage. We predicted that for juvenile plants, mortality would be higher for P. lanceolata than for L. perenne, because the thin taproot of P. lanceolata is less tolerant to herbivory. We hypothesized that for mature plants, herbivory of fibrous roots would negatively affect biomass; thus, L. perenne would be less tolerant than P. lanceolata. Plants of L. perenne or P. lanceolata at four ages were grown in pots with or without a herbivore. Herbivores killed juvenile plants, but not mature plants, of both species. More juveniles of P. lanceolata than L. perenne were killed by herbivory. In P. lanceolata, the low biomass of juveniles was attributed to herbivory, but herbivory did not affect the biomass of mature plants. In contrast, herbivory negatively affected the biomass of L. perenne plants of all ages. We concluded that the effects of belowground herbivory depend on plant age and, thus, on plant growth stage and root architecture.

Isolation and Characterization of a Defensin-Like Peptide (Coprisin) from the Dung Beetle, Copris tripartitus

The antibacterial activity of immune-related peptides, identified by a differential gene expression analysis, was investigated to suggest novel antibacterial peptides. A cDNA encoding a defensin-like peptide, Coprisin, was isolated from bacteria-immunized dung beetle, Copris tripartitus, by using differential dot blot hybridization. Northern blot analysis showed that Coprisin mRNA was up-regulated from 4 hours after bacteria injection and its expression level was reached a peak at 16 hours. The deduced amino acid sequence of Coprisin was composed of 80 amino acids with a predicted molecular weight of 8.6 kDa and a pI of 8.7. The amino acid sequence of mature Coprisin was found to be 79.1% and 67.4% identical to those of defensin-like peptides of Anomala cuprea and Allomyrina dichotoma, respectively. We also investigated active sequences of Coprisin by using amino acid modification. The result showed that the 9-mer peptide, LLCIALRKK-NH2, exhibited potent antibacterial activities against Escherichia coli and Staphylococcus aureus.

The N-Terminal Region of an Entomopoxvirus Fusolin Is Essential for the Enhancement of Peroral Infection, whereas the C-Terminal Region Is Eliminated in Digestive Juice

ABSTRACT The spindles of Anomala cuprea entomopoxvirus (AncuEPV), which are composed of glycoprotein fusolin, are known to enhance the peroral infectivity of AncuEPV itself and of nucleopolyhedroviruses. This has been demonstrated to involve the disruption of intestinal peritrophic membrane (PM), composed of chitin matrix, glycosaminoglycans, and proteins. To identify essential and nonessential regions for this enhancement activity, AncuEPV fusolin and its deletion mutants were expressed in Sf21 cells using a baculovirus system, and their enhancement abilities were analyzed. The recombinant fusolin enhanced the peroral infectivity of Bombyx mori nucleopolyhedrovirus up to 320-fold and facilitated the infection of host insect with AncuEPV. Deletion mutagenesis revealed that the N-terminal region (amino acids 1 to 253), a possible chitin-binding domain, is essential for the enhancement of infection, whereas the C-terminal region is entirely dispensable. The glycosylation-defective mutants N191Q, whose Asn191 is replaced with Gln, and ΔSIG, whose signal peptide is deleted, showed considerably reduced and abolished enhancing activities, respectively, indicating that the carbohydrate chain is important in the enhancing activity. Interestingly, the C-terminal dispensable region was digested by a serine protease(s) in insect digestive juice. Moreover, both the N-terminal conserved region and the carbohydrate chain were necessary not only for chitin binding but also for stability in digestive juice. A triple amino acid replacement mutant, IHE (Ile-His-Glu161 to Ala-Ala-Ala), was stable in digestive juice and had chitin-binding ability but did not retain its enhancing activity. These results suggest that the enhancement of infectivity involves more than the tolerance to digestive juice and chitin-binding ability.