Commercial biotechnology solutions for controlling lepidopteran and coleopteran insect pests on crops depend on the expression of Bacillus thuringiensis insecticidal proteins, most of which permeabilize the membranes of gut epithelial cells of susceptible insects. However, insect control strategies involving a different mode of action would be valuable for managing the emergence of insect resistance. Toward this end, we demonstrate that ingestion of double-stranded (ds)RNAs supplied in an artificial diet triggers RNA interference in several coleopteran species, most notably the western corn rootworm (WCR) Diabrotica virgifera virgifera LeConte. This may result in larval stunting and mortality. Transgenic corn plants engineered to express WCR dsRNAs show a significant reduction in WCR feeding damage in a growth chamber assay, suggesting that the RNAi pathway can be exploited to control insect pests via in planta expression of a dsRNA.

The genetic basis of variation in obesity in human populations is thought to be owing to many genes of relatively small effect and their interactions. The LG/J by SM/J intercross of mouse inbred strains provides an excellent model system in which to investigate multigenic obesity. We previously mapped a large number of quantitative trait loci (QTLs) affecting adult body weight in this cross. We map body composition traits, adiposity, and skeletal size, in a replicate F2 intercross of the same two strains containing 510 individuals. Using interval-mapping methods, we located eight QTLs affecting adiposity (Adip1-8). Two of these adiposity loci also affected tail length (Adip4 and Adip6) along with seven additional tail length QTLs (Skl1-7). A further four QTLs (Wt1-4) affect adult weight but not body composition. These QTLs have relatively small effects, typically about 0.2-0.4 standard deviation units, and account for between 3% and 10% of the variance in individual characters. All QTLs participated in epistatic interactions with other QTLs. Most of these interactions were due to additive-by-additive epistasis, which can nullify the apparent effects of single loci in our population. Adip8 interacts with all the other adiposity QTLs and seems to play a central role in the genetic system affecting obesity in this cross. Only two adiposity QTLs, Adip4 and Adip6, also affect tail length, indicating largely separate genetic control of variation in adiposity and skeletal size. Body size and obesity QTLs in the same locations as those discovered here are commonly found in mapping experiments with other mouse strains.

Over 20 years ago, D. S. Falconer and others launched an important avenue of research into the quantitative of body size growth in mice. This study continues in that tradition by locating quantitative trait loci (QTLs) responsible for murine growth, such as age-specific weights and growth periods, and examining the genetic architecture for body weight. We identified a large number of potential QTLs in an earlier F2 intercross (Intercross I) of the SM/J and LG/J inbred mouse strains. Many of these QTLs are replicated in a second F2 intercross (Intercross II) between the same two strains. These replicated regions provide candidate regions for future fine-mapping studies. We also examined body size and growth QTLs using the combined data set from these two intercrosses, resulting in 96 microsatellite markers being scored for 1045 individuals. An examination of the genetic architecture for age-specific weight and growth periods resulted in locating 20 separate QTLs, which were mainly additive in nature, although dominance was found to affect early growth and body size. QTLs affecting early and late growth were generally distinct, mapping to separate chromosome locations. This QTL pattern indicates largely separate genetic and physiological systems for early and later murine growth, as Falconer suggested. We also found sex-specific QTLs for body size with implications for the evolution of sexual dimorphism.

uses a variant Bt Cry3Bb1 insecticidal protein (Donovan et al., 1992). Cry3Bb1 is known to be biologically active The corn rootworm (CRW; Diabrotica spp.) is one of the most against several species within the Coleopteran family serious pests of corn in the USA. Chemical insecticides and crop rotation have been the only two options available to growers for Chrysomelidae, including the western corn rootworm, managing CRW. Unfortunately, both of these tactics can be ineffective Diabrotica virgifera virgifera LeConte (Rupar et al., as a result of either resistance or behavioral modifications. In this 1991). The biological activity of this protein against D. paper, we describe transgenic maize (Zea mays L.) hybrids that control virgifera virgifera suggested its potential use in creating CRW. These hybrids were created with a Cry3Bb1 Bacillus thurintransgenic plants expressing Cry3Bb1 that would confer giensis (Bt) variant that is approximately eight times more lethal to protection to corn root tissue from larval feeding damcorn rootworm larvae than the wild-type protein. A DNA vector age. To further augment protection of the root system containing the modified cry3Bb1 gene was placed under control of a from larval feeding damage, modifications were introroot-enhanced promoter (4-AS1) and was introduced into embryonic duced in the cry3Bb1 gene that gave rise to an amino acid maize cells by microprojectile bombardment. Described here is the variant Cry3Bb1 protein with an eight-fold increase in molecular genetic characterization, protein expression levels, and field performance of the recently commercialized MON863 hybrids.

Pleiotropy refers to a single genetic locus that affects more than one phenotypic trait. Pleiotropic effects of genetic loci are thought to play an important role in evolution, reflecting functional and developmental relationships among phenotypes. In a previous study, we examined pleiotropic effects displayed by quantitative trait loci (QTLs) on murine mandibular morphology in relation to mandibular structure and function. In replicating most of our previous QTLs and increasing our sample size, this study strengthens and extends our earlier results. As in our previous study, we find that QTL effects tend to be restricted to developmentally or functionally related traits. In addition, we examine patterns of differential dominance for pleiotropic QTL effects. Differential dominance occurs when dominance patterns for a single locus vary among traits. We find that multivariate overdominance is a common and substantial phenomenon, and may potentially provide an explanation for the persistence of heterozygosity in natural populations.

Strain intercross experiments provide a powerful means for mapping genes affecting complex quantitative traits. We report on the genetic variability of the intercross of the Large (LG/J) and Small (SM/J) inbred mouse strains as a guide to gene mapping studies. Ten SM/J males were crossed to 10 LG/J females, after which animals were randomly mated to produce F1, F2, and F3 intercross generations. The 1632 F3 animals from 200 full-sib families were used to estimate heritabilities and genetic correlations of the traits measured. A subset of families was cross-fostered at birth to allow measurement of the importance of post-natal maternal effects. Data was collected on weekly body weight from one to 10 weeks and on organ weights, body weight, reproductive fat pad weight, and tail length at necropsy in the intercross generations. There was no heterosis for age-specific weights or necropsy traits, except that one-week weight was the highest in the F2 generation, indicating heterosis for maternal effect in the F1 mothers. We found moderate to high heritability for most age-specific weights and necropsy traits. Maternal effects were significant for age-specific weights from one to four weeks but disappeared completely at ten-week weight. Maternal effects for necropsy traits were low and not statistically significant. Age-specific weights showed a typical correlation pattern, with correlation declining as the difference in ages increased. Among necropsy traits, reproductive fat pad and body weights were very highly genetically correlated. Most other genetic correlations were low to moderate. The intercross between SM/J and LG/J inbred mouse strains provides a valuable resource for mapping quantitative trait loci for body size, composition, and morphology
Os experimentos de intercruzamento de cepas constituem um valioso meio de mapear genes que afetam caracteres quantitativos complexos. Nós estudamos a variabilidade genética do intercruzamento das cepas procriadas por endogamia de camundongos Large (LG/J) e Small (SM/J), como um guia para estudos de mapeamento gênico. Dez machos SM/J foram cruzados com 10 fêmeas LG/J, após o que os animais foram acasalados aleatoriamente para produzir as gerações intercruzadas F1, F2 e F3. Os 1632 animais da geração F3 das 200 famílias de irmãos completos foram usados para calcular a herdabilidade e as correlações genéticas dos caracteres medidos. Um subgrupo de famílias foi submetido a adoção cruzada após o nascimento, para permitir a avaliação da importância dos efeitos maternos pós-natais. Foram coletados dados semanais de peso corporal da 1ª à 10ª semanas, assim como dados de necropsia do peso corporal, peso de órgãos, peso do coxim gorduroso reprodutor e comprimento de cauda nas gerações intercruzadas. Não houve heterose para pesos específicos para idade ou caracteres de necropsia, exceto pelo fato de que o peso da 1ª semana foi o maior na geração F2, indicando heterose dos efeitos maternos nas mães da geração F1. Encontramos herdabilidade moderada/alta para a maioria dos pesos esp...

Do body size components, such as weights of internal organs and long bone lengths, with different functions and different developmental histories also have different genetic architectures and pleiotropic patterns? We examine murine quantitative trait loci (QTL) for necropsy weight, four long bone lengths, and four organ weights in the LG/J x SM/J intercross. Differences between trait categories were found in number of QTL, dominance, and pleiotropic patterns. Ninety-seven QTLs for individual traits were identified: 52 for long bone lengths, 30 for organ weights, and 15 for necropsy weight. Results for long bones are typically more highly significant than for organs. Organ weights were more frequently over- or underdominant than long bone lengths or necropsy weight. The single-trait QTLs map to 35 pleiotropic loci. Long bones are much more frequently affected in groups while organs tend to be affected singly or in pairs. Organs and long bones are found at the same locus in only 11 cases, 8 of which also include necropsy weight. Our results suggest mainly separate genetic modules for organ weights and long bone lengths, with a few loci that affect overall body size. Antagonistic pleiotropy, in which a locus has opposite effects on different characteristics, is uncommon.

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