Heat Shock Protein 83 (Hsp83) Facilitates Methoprene-tolerant (Met) Nuclear Import to Modulate Juvenile Hormone Signaling

Juvenile hormone (JH) receptors, methoprene-tolerant (Met) and Germ-cell expressed (Gce), transduce JH signals to induce Kr-h1 expression in Drosophila. Dual luciferase assay identified a 120-bp JH response region (JHRR) in the Kr-h1α promoter. Both in vitro and in vivo experiments revealed that Met and Gce transduce JH signals to induce Kr-h1 expression through the JHRR. DNA affinity purification identified chaperone protein Hsp83 as one of the proteins bound to the JHRR in the presence of JH. Interestingly, Hsp83 physically interacts with PAS-B and basic helix-loop-helix domains of Met, and JH induces Met-Hsp83 interaction. As determined by immunohistochemistry, Met is mainly distributed in the cytoplasm of fat body cells of the larval when the JH titer is low and JH induces Met nuclear import. Hsp83 was accumulated in the cytoplasm area adjunct to the nucleus in the presence of JH and Met/Gce. Loss-of-function of Hsp83 attenuated JH binding and JH-induced nuclear import of Met, resulting in a decrease in the JHRR-driven reporter activity leading to reduction of Kr-h1 expression. These data show that Hsp83 facilitates the JH-induced nuclear import of Met that induces Kr-h1 expression through the JHRR.     

Pleiotropic Effects of methoprene-tolerant(Met), a Gene Involved in Juvenile Hormone Metabolism, on Life History Traits in Drosophila melanogaster

Life history theory assumes that there are alleles with pleiotropic effects on fitness components. Although quantitative genetic data are often consistent with pleiotropy, there are few explicit examples of pleiotropic loci. The Drosophila melanogaster gene Methoprene-tolerant (Met) may be such a locus. The Met gene product, a putative juvenile hormone receptor, facilitates the action of juvenile hormone (JH) and JH analogs; JH affects many life history traits in arthropods. Here we use quantitative complementation to investigate effects of Met mutant and wildtype alleles on female developmental time, onset of reproduction, and fecundity. Whereas the alleles did not differ in their effects on developmental time, we detected allelic variation for the onset of reproduction and for age-specific fecundity. Alleles influenced phenotypic co-variances among traits (developmental time and onset of reproduction; onset of reproduction and both early and late fecundity; early and late fecundity), suggesting that alleles of Met vary in their pleiotropic effects upon life history. Furthermore, the genetic covariance between developmental time and early fecundity attributed to alleles of Met was negative, indicating consistent pleiotropic effects among alleles on these traits. The allelic effects of Met support genetic models where pleiotropy at genes associated with hormone regulation can contribute to the evolution of life history traits.     

Effect of the Juvenile Hormone Analog,Fenoxycarb on Termination of Reproductive Diapause in Scotinophara lurida (Burmeister) (Heteroptera: Pentatomidae)

This study was carried out to investigate a role of the juvenile hormone analog, fenoxycarb (FC) in terminating the reproductive diapause in the black rice bug, Scotinophara lurida (Burmeister) (Heteroptera: Pentatomidae). FC-treated adults collected at different dates developed their ovaries sooner than untreated ones. Topical application of FC accelerated diapause termination of field-collected S. lurida in which FC-treated adults exhibited early oviposition. In FC-treated males, development of their accessory glands and testes accelerated appeared to be prompted. These results suggest that various physiological overwintering traits related to diapause in this species may in part be under gonadotrophic endocrine control.     

Genetic Evidence for Function of the bHLH-PAS Protein Gce/Met As a Juvenile Hormone Receptor

Juvenile hormones (JHs) play a major role in controlling development and reproduction in insects and other arthropods. Synthetic JH-mimicking compounds such as methoprene are employed as potent insecticides against significant agricultural, household and disease vector pests. However, a receptor mediating effects of JH and its insecticidal mimics has long been the subject of controversy. The bHLH-PAS protein Methoprene-tolerant (Met), along with its Drosophila melanogaster paralog germ cell-expressed (Gce), has emerged as a prime JH receptor candidate, but critical evidence that this protein must bind JH to fulfill its role in normal insect development has been missing. Here, we show that Gce binds a native D. melanogaster JH, its precursor methyl farnesoate, and some synthetic JH mimics. Conditional on this ligand binding, Gce mediates JH-dependent gene expression and the hormone''s vital role during development of the fly. Any one of three different single amino acid mutations in the ligand-binding pocket that prevent binding of JH to the protein block these functions. Only transgenic Gce capable of binding JH can restore sensitivity to JH mimics in D. melanogaster Met-null mutants and rescue viability in flies lacking both Gce and Met that would otherwise die at pupation. Similarly, the absence of Gce and Met can be compensated by expression of wild-type but not mutated transgenic D. melanogaster Met protein. This genetic evidence definitively establishes Gce/Met in a JH receptor role, thus resolving a long-standing question in arthropod biology.     

The Experimental Assessment of Fitness in Drosophila. II. a Comparison of Competitive and Noncompetitive Measures

Twelve diverse strains of Drosophila melanogaster have been examined with respect to their individual fitness components and with respect to their relative performance under competitive and noncompetitive conditions. Individual fitness components included estimates of time until successful copulation (t), fecundity (f) and egg-to-adult viability (v), and a composite index of overall fitness of the form fv/t was used for comparisons among strains. Noncompetitive performance was assessed in terms of the biomass (standing crop) and productivity of equilibrium experimental populations. Competitive performance was assessed in terms of relative competitive ability vis-à-vis a standard compound-autosome-bearing strain in single-generation tests. A significant correlation was found between the composite index of individual fitness components and the competitive compound-autosome test. Although the biomass and productivity of equilibrium populations were correlated with each other, neither of these noncompetitive measures was correlated with individual fitness components or with the composite index. We suggest that the performance of strains in such noncompetitive tests may be related to what Wright has called the "mean selective value" of the populations. Judging from their association with the composite index of individual fitness components, competitive tests such as the compound-autosome test seem to be related more nearly to the average Darwinian fitness of the populations.     

烟草抗黑胫病突变体的细胞筛选

经实验我们成功地建立了在细胞水平上筛选烟草抗黑胫病突变体的筛选体系。该体系的主要内容为:γ-射线500—2000拉德诱变高度感病品种的花药后用50—80％的黑胫病菌粗毒素为选择压力,筛选出抗毒素花粉植株,用离体叶片法测定选出抗病植株,再从后代鉴定中选出抗病性能够稳定遗传的突变系。γ-射线及高浓度毒素处理均能得到抗病植株。选自感病品种的花粉植株中约有9—50％是真正抗病的。这些抗病植株中有一部分的抗病性能够稳定遗传。用该法已从感病优质品种小黄金1025及乔庄黑苗中选出6个突变系。并自N.C.628(抗)×小黄金1025(感)及N.C.628(抗)×庆胜2号(感)的F_1花粉植株中选出4个抗病系。所有的抗病系经3—4代后均表现出稳定抗性。其中一个突变体(R400)的抗性似由不完全显性多基因控制。     

Retrotransposon-Induced Ectopic Expression of Cut Causes the Om(1a) Mutant in Drosophila Ananassae

Optic morphology (Om) mutations in Drosophila ananassae map to at least 22 loci scattered throughout the genome. They are semidominant, neomorphic, nonpleiotropic, and are associated with the insertion of a retrotransposon, tom. The Om(1A) gene, which is cytogenetically linked to the cut locus, was cloned using a DNA fragment of the cut locus of Drosophila melanogaster as a probe. Three of the eight alleles of Om(1A) examined have insertion of the tom element within a putative cut region. The γ-ray-induced revertants of Om(1A) are accompanied with cut lethal mutations and rearrangements within the cut coding region. In the eye imaginal discs of the Om(1A) mutants, differentiation of photoreceptor clusters is suppressed, abnormal cell death occurs in the center and the cut protein is expressed ectopically. D. melanogaster flies transformed with a chimeric cut gene under the control of a heat-inducible promoter show excessive cell death in the region anterior to the morphogenetic furrow, suppressed differentiation to photoreceptor clusters and defect in the imaginal eye morphology when subjected to temperature elevation. These findings suggest that the tom element inserted within the Om(1A) region induces ectopic cut expression in the eye imaginal discs, thus resulting in the Om(1A) mutant phenotype.     

The Effect of Radiation-Induced Mutations on the Fitness of Drosophila Populations

The change in frequencies of D. melanogaster and D. simulans in competition experiments was used to measure the effect of radiation on the fitness of a population. A dose of 250 or 500 rads given to the males of highly inbred lines of D. simulans at the beginning of competition and every three weeks thereafter increased the relative frequency of the irradiated population. If the dose was increased to 1000 rads, the deleterious effects of radiation became too great a burden on the population, and the frequency of the irradiated population decreased. From these results it was concluded that below certain doses the introduction of radiation-induced mutations into a highly homozygous population would increase the fitness of the population.     

Physiological and Structural Differences Between Enterococcus faecalis JH2-2 and Mutant Strains Resistant to (P)-Divercin RV41

The aim of this study was to show the differences that could exist at the physiological and structural levels between Enterococcus faecalis JH2-2 (wild type) and three mutant strains resistant to divercin RV41. These mutant strains were recently isolated and characterized for their intermediate resistance to recombinant DvnRV41; a subclass IIa bacteriocin produced by Escherichia coli. These mutant strains were named 35A1 (altered in gene coding phosphoesterase activity), 35H1 (altered in gene coding σ⁵⁴ factor) and 36H4 (altered in gene coding glycerophosphodiesterase). The growth and resistance of each strain were tested against lysozyme. The inhibitory substance did not show any cross-resistance but exhibited an additive effect ascribed to the combined action of lysozyme and (P)-DvnRV41. The use of Fourier transform infrared spectroscopy (FT-IR) allowed to unravelling differences at the structural levels between the aforementioned strains. Thus, mutants 35H1 and 36H4 showed clear differences from mutant 35A1 and wild-type strain. These differences were located, mainly in the fatty acid region and in the polysaccharide composition. This study contributes to understanding more the resistance/sensitivity of Ent. faecalis to (P)-DvnRV41, a subclass IIa bacteriocin.     

Two peptidases that convert 125I-Lys-Arg(Met)enkephalin and 125I-(Met)enkephalin-Arg6, respectively,to 125I-(Met)enkephalin in bovine adrenal medullary chromaffin granules

Two peptidases which convert ¹²⁵I-Lys-Arg-ME and ¹²⁵I-ME-Arg⁶, respectively, to ¹²⁵I-ME, have been identified and characterized in bovine adrenomedullary chromaffin granules. The former is referred to as a secretory granule peptidase (SGP) and the latter as a carboxypeptidase B-like enzyme (CPB-like) [7] which is here further characterized. SGP cleaved ¹²⁵I-Lys-Arg-ME to produce only ¹²⁵I-ME and was localized in chromaffin granules which contained co²⁺-stimulated CPB-like activity, ME, and catecholamines. Both the SGP and the CPB-like enzymes appear to be thiol-metalloproteases. While the CPB-like enzyme seems likely to be involved in processing the enkephalin precursors [7], SGP may function as a trypsin-like or aminopeptidase enzyme in secretory granules.