Opposite sex-specific effects of Wolbachia and interference with the sex determination of its host Ostrinia scapulalis

In the adzuki bean borer, Ostrinia scapulalis, the sex ratio in most progenies is 1 : 1. Females from Wolbachia-infected matrilines, however, give rise to all-female broods when infected and to all-male broods when cured of the infection. These observations had been interpreted as Wolbachia-induced feminization of genetic males into functional females. Here, we show that the interpretation is incorrect. Females from both lines have a female karyotype with a WZ sex-chromosome constitution while males are ZZ. At the time of hatching from eggs, WZ and ZZ individuals are present at a 1 : 1 ratio in broods from uninfected, infected and cured females. In broods from Wolbachia-infected females, ZZ individuals die during larval development, whereas in those from cured females, WZ individuals die. Hence, development of ZZ individuals is impaired by Wolbachia but development of WZ females may require the presence of Wolbachia in infected matrilines. Sexual mosaics generated (i) by transfection of uninfected eggs and (ii) by tetracycline treatment of Wolbachia-infected mothers prior to oviposition were ZZ in all tissues, including typically female organs. We conclude that: (i) Wolbachia acts by manipulating the sex determination of its host; and (ii) although sexual mosaics can survive, development of a normal female is incompatible with a ZZ genotype.     

Proregion of Bombyx mori cysteine proteinase functions as an intramolecular chaperone to promote proper folding of the mature enzyme.

A cDNA encoding the proform of Bombyx cysteine proteinase (BCP) was expressed at a high level in Escherichia coli using the T7 polymerase expression system. The insoluble recombinant zymogen was solubilized and renatured by modifying a method applied to human pro-cathepsin L. Like the natural BCP precursor, the recombinant proenzyme was spontaneously converted to an active proteinase at pH 3.75. A deletion in the central region of the propeptide resulted in much loss of the activity, suggesting that the propeptide is essential for proper folding during renaturation. In contrast, the renatured mature form of recombinant BCP was not active but regained activity by including the propeptide in the renaturing buffer, suggesting that the propeptide, acting as an intramolecular chaperone, promotes refolding of the associated proteinase domain into an active conformation. The mature form of natural BCP rapidly lost its activity at neutral pH, whereas its proform was stable. The mature enzyme retained some activity in the presence of the propeptide. Arch.     

Dual Designs and Their Application in Genetical Experiments

The dual of incomplete block designs has been studied with th́eir applications in genetical experiments. Partial diallel crosses (PDC) of type I have been constructed using balanced incomplete block (BIB) designs, partially balanced incomplete block (PBIB) designs and their dual designs. Simplified analysis of PDC has been presented using the dual property of these designs. List of optimal PDC having simple analysis has been given.     

Double trouble: combined action of meiotic drive and Wolbachia feminization in Eurema butterflies

Arthropod sex ratios can be manipulated by a diverse range of selfish genetic elements, including maternally inherited Wolbachia bacteria. Feminization by Wolbachia is rare but has been described for Eurema mandarina butterflies. In this species, some phenotypic and functional females, thought to be ZZ genetic males, are infected with a feminizing Wolbachia strain, wFem. Meanwhile, heterogametic WZ females are not infected with wFem. Here, we establish a quantitative PCR assay allowing reliable sexing in three Eurema species. Against expectation, all E. mandarina females, including wFem females, had only one Z chromosome that was paternally inherited. Observation of somatic interphase nuclei confirmed that W chromatin was absent in wFem females, but present in females without wFem. We conclude that the sex bias in wFem lines is due to meiotic drive (MD) that excludes the maternal Z and thus prevents formation of ZZ males. Furthermore, wFem lines may have lost the W chromosome or harbour a dysfunctional version, yet rely on wFem for female development; removal of wFem results in all-male offspring. This is the first study that demonstrates an interaction between MD and Wolbachia feminization, and it highlights endosymbionts as potentially confounding factors in MD of sex chromosomes.     

Dexamethasone stimulates the expression of ghrelin and its receptor in rat hypothalamic 4B cells

Growth hormone (GH)-releasing peptides (GHRPs) are synthetic peptides that strongly induce GH release. GHRPs act via a specific receptor, the GHRP receptor (GHSR), of which ghrelin is a natural ligand. GHRPs also induce adrenocorticotropic hormone (ACTH) release in healthy subjects. GHRPs or ghrelin stimulate ACTH release via corticotropin-releasing factor (CRF) and arginin vasopressin in the hypothalamus. Stress-activated CRF neurons are suppressed by glucocorticoids in the hypothalamic paraventricular nucleus (PVN), while CRF gene is up-regulated by glucocorticoids in the PVN cells without the influence of input neurons. However, little is known about the regulation of ghrelin and GHSR type 1a (GHSR1a) genes by glucocorticoids in PVN cells. To elucidate the regulation of ghrelin and GHSR gene expression by glucocorticoids in PVN cells, here we used a homologous PVN neuronal cell line, hypothalamic 4B, because these cells show characteristics of the parvocellular neurons of the PVN. These cells also express ghrelin and GHSR1a mRNA. Dexamethasone increased ghrelin mRNA levels. A potent glucocorticoid receptor antagonist, RU-486, significantly blocked dexamethasone-induced increases in ghrelin mRNA levels. Dexamethasone also significantly stimulated GHSR1a mRNA and protein levels. Finally, ghrelin increased CRF mRNA levels, as did dexamethasone. Incubation with both dexamethasone and ghrelin had an additive effect on CRF and ghrelin mRNA levels. The ghrelin-GHSR1a system is activated by glucocorticoids in the hypothalamic cells.     

Life Cycle of <Emphasis Type="Italic">Plasmodiophora brassicae</Emphasis>

Plasmodiphora brassicae is a soil-borne obligate parasite. The pathogen has three stages in its life cycle: survival in soil, root hair infection, and cortical infection. Resting spores of P. brassicae have a great ability to survive in soil. These resting spores release primary zoospores. When a zoospore reaches the surface of a root hair, it penetrates through the cell wall. This stage is termed the root hair infection stage. Inside root hairs the pathogen forms primary plasmodia. A number of nuclear divisions occur synchronously in the plasmodia, followed by cleavage into zoosporangia. Later, 4–16 secondary zoospores are formed in each zoosporangium and released into the soil. Secondary zoospores penetrate the cortical tissues of the main roots, a process called cortical infection. Inside invaded roots cells, the pathogen develops into secondary plasmodia which are associated with cellular hypertrophy, followed by gall formation in the tissues. The plasmodia finally develop into a new generation of resting spores, followed by their release back into soil as survival structures. In vitro dual cultures of P. brassicae with hairy root culture and suspension cultures have been developed to provide a way to nondestructively observe the growth of this pathogen within host cells. The development of P. brassicae in the hairy roots was similar to that found in intact plants. The observations of the cortical infection stage suggest that swelling of P. brassicae-infected cells and abnormal cell division of P. brassicae-infected and adjacent cells will induce hypertrophy and that movement of plasmodia by cytoplasmic streaming increases the number of P. brassicae-infected cells during cell division.     

Galanin-like peptide and the regulation of feeding behavior and energy metabolism

The hypothalamic neuropeptides modulate physiological activity via G protein-coupled receptors (GPCRs). Galanin-like peptide (GALP) is a 60 amino acid neuropeptide that was originally isolated from porcine hypothalamus using a binding assay for galanin receptors, which belong to the GPCR family. GALP is mainly produced in neurons in the hypothalamic arcuate nucleus. GALP-containing neurons form neuronal networks with several other types of peptide-containing neurons and then regulate feeding behavior and energy metabolism. In rats, the central injection of GALP produces a dichotomous action that involves transient hyperphasia followed by hypophasia and a reduction in body weight, whereas, in mice, it has only one action that reduces both food intake and body weight. In the present minireview, we discuss current evidence regarding the function of GALP, particularly in relation to feeding and energy metabolism. We also examine the effects of GALP activity on food intake, body weight and locomotor activity after intranasal infusion, a clinically viable mode of delivery. We conclude that GALP may be of therapeutic value for obesity and life-style-related diseases in the near future.