Differential expression of cuticle-epidermis proteins in the shrimp Penaeus vannamei during molting

Proteomic and microscopic approaches in understanding mechanisms of shell-loosening of shrimp (Pandalus borealis) induced by high pressure and protease

Shell-loosening is of importance in facilitating shrimp peeling. In this study, enzyme and high pressure (HP) improved the shell-loosening at different degrees, which were observed as gaps by microscopy. The shell-loosening gap induced by an endoprotease with broad specificity (Endocut-03L, 53 μm) was much higher than that induced by HP at 100 MPa (HP100, 12 μm), followed by an endoprotease with high specificity (Tail21, 8 μm), and HP at 600 MPa (HP600, 5 μm). The degree of shell-loosening was found to be correlated to the extent of protein changes that were obtained by 2D gel electrophoresis. Shell-loosening due to HP100 and Endocut-03L was mainly caused by physical and enzymatic degradation of high molecular-weight proteins in shell and epidermis and subsequent loss of degradation products, disrupting the structure of muscle-shell connection. However, HP100 was less effective than Endocut-03L due to its stabilizing effect on the shell collagen, lowering its shell-loosening effect.

Cyclodiene insecticide resistance: from molecular to population genetics

This review follows progress in the analysis of cyclodiene insecticide resistance from the initial isolation of the mutant, through cloning of the resistance gene, to an examination of the distribution of resistance alleles in natural populations. Emphasis is given to the use of a resistant Drosophila mutant as an entry point to cloning the associated gamma-aminobutyric acid (GABA) receptor subunit gene, Resistance to dieldrin. Resistance is associated with replacements of a single amino acid (alanine302) in the chloride ion channel pore of the protein. Replacements of alanine302 not only directly affect the drug binding site but also allosterically destabilize the drug preferred conformation of the receptor. Resistance is thus conferred by a unique dual mechanism associated with alanine302, which is the only residue replaced in a wide range of different resistant insects. The underlying mutations appear either to have arisen once, or multiply, depending on the population biology of the pest insect. Although resistance frequencies decline in the absence of selection, resistance alleles can persist at relatively high frequency and may cause problems for compounds to which cross-resistance is observed, such as the novel fipronils.

Molecular biology of insect neuronal GABA receptors

Ionotropic gamma-aminobutyric acid (GABA) receptors are distributed throughout the nervous systems of many insect species. As with their vertebrate counterparts, GABAA receptors and GABAC receptors, the binding of GABA to ionotropic insect receptors elicits a rapid, transient opening of anion-selective ion channels which is generally inhibitory. Although insect and vertebrate GABA receptors share a number of structural and functional similarities, their pharmacology differs in several aspects. Recent studies of cloned Drosophila melanogaster GABA receptors have clarified the contribution of particular subunits to these differences. Insect ionotropic GABA receptors are also the target of numerous insecticides and an insecticide-resistant form of a Drosophila GABA-receptor subunit has enhanced our understanding of the structure-function relationship of one aspect of pharmacology common to both insect and vertebrate GABA receptors, namely antagonism by the plant-derived toxin picrotoxinin.