Ovarian ecdysteroid biosynthesis and female germline stem cells

The germline stem cells (GSCs) are critical for gametogenesis throughout the adult life. Stem cell identity is maintained by local signals from a specialized microenvironment called the niche. However, it is unclear how systemic signals regulate stem cell activity in response to environmental cues. In our previous article, we reported that mating stimulates GSC proliferation in female Drosophila. The mating-induced GSC proliferation is mediated by ovarian ecdysteroids, whose biosynthesis is positively controlled by Sex peptide signaling. Here, we characterized the post-eclosion and post-mating expression pattern of the genes encoding the ecdysteroidogenic enzymes in the ovary. We further investigated the biosynthetic functions of the ovarian ecdysteroid in GSC maintenance in the mated females. We also briefly discuss the regulation of the ecdysteroidogenic enzyme-encoding genes and the subsequent ecdysteroid biosynthesis in the ovary of the adult Drosophila.     

果蝇求偶行为的影响因素及其分子基础

果蝇Drosophila melanogaster Meigen是进行行为遗传学研究的极好材料。果蝇的雄性求偶行为已经被作为行为遗传学研究的模式。文章简要介绍近年来在遗传和分子水平上对果蝇性信息素和求偶行为的研究进展,尤其是突变体在果蝇行为遗传学研究中的应用。通过对果蝇求偶行为的分析,分别介绍果蝇的性信息素及视觉、听觉、嗅觉和味觉相关基因在果蝇求偶和交配行为过程中的作用。     

Onion fly,Delia antiqua,oviposition and mating as influenced by insect age and dosage of male reproductive tract extract (Diptera: Anthomyiidae)

One hundred percent of virgin female onion flies,Delia antiqua, receiving 1/20 of a male equivalent of an aqueous extract of mature male reproductive tract remained unmated in the presence of males and began laying unfertilized eggs at a normally mated rate of about 20 eggs/female/day. The 50% behavioral response (BR₅₀) fell between 1/40 and 1/20 of a male equivalent. Sex peptide responses are not always all-or-none. Some females receiving extract at 1/40 male equivalent oviposited at an intermediate rate. Moreover, at low sex peptide dosages, some females were fully activated ovipositionally but were receiptive to mating. A low level of sex peptide was present in 1-day-old males. Sex peptide titer rose with age until plateauing by 6 days posteclosion. Males began mating at 3 days, when they first had ample mature sperm; 50% of 6-day-old males mated. The mean number of females inseminated per male exposed to an excess of virgin females over 24 h was 4.3±0.6 (±SE). Presence of mature eggs was not always a prerequisite for mating, although probability of insemination was correlated with egg maturation. One-day-old preovipositional females receiving 1/20 of a male equivalent of extract began ovipositing when they had mature eggs at 5–6 days old. Therefore, sex peptide may act early and permanently or have a long half-life and affect behaviors once females reach sexual maturity. Male flies provide females with an excess of sex peptide in many cases.D. antiqua males transferred ca. 5–10 times more sex peptide than necessary to activate females fully. We suggest this excess is related to the speed of female response. It is yet unclear whether sex peptide potency or titer in Diptera has become exaggerated by intra- or intersexual selection.     

Modification of female onion fly,Delia antiqua (Meigen), reproductive behavior by male paragonial gland extracts (Diptera: Anthomyiidae)

Egg depositional rates of onion flies, Delia antiqua(Meigen), injected thoracically with extracts of male paragonial glands were identical (14.5 eggs/female/ day) to those of normally mated females. Moreover, when continuously exposed to males, extract-injected females refused to mate and produced unfertilized eggs for the duration of the > 15- day experiment. For this normally monocoitic dipteran, <1 male equiv of paragonial secretion completely reproduced the ovipositional responses characteristic of normal mating, and this effect required no involvement of the genitalia or genital chamber. We suggest that the receptor for the active chemical (s) (sex peptide?) would be an excellent target for biorational insect control by sterilization. Moreover, these primer sex pheromones might play an important role in insect reproductive isolation and evolution.     

Remating and sperm displacement in a natural population of Drosophila buzzatii inferred from mother-offspring analysis of microsatellite loci

Prospects for estimation of parameters of models of sperm competition from field data have improved recently with the development of methods that employ multilocus genotype data from brood-structured samples. Sperm competition in Drosophila buzzatii is of special interest because it is possible to directly observe the breeding behaviour of this species in its natural habitat of rotting cactus. Previous laboratory experiments showed that this species exhibits an unusual pattern of frequent remating and sperm partitioning. This paper reports the first attempt to estimate the frequency of female remating and sperm competition in natural populations of D. buzzatii. For the Australian population studied, the mean remating frequency was lower (alpha = 2.12-2.20) than previously estimated in laboratory experiments with the same population, whereas mean sperm displacement (beta = 0.69-0.71) fell within the limits of previous laboratory results. The evolution of the D. buzzatii mating system is discussed.     

Female remating inDrosophila ananassae: shorter duration of copulation during second mating as compared to first mating

Drosophila ananassae, a cosmopolitan and domestic species, belongs to theananassae subgroup of themelanogaster species group. Female remating was observed in ten mass culture stocks of this species, which were initiated from flies collected from different geographic localities. The frequency of female remating ranges from 24% to 56% in different strains. Strains show significant variation in remating latency (days). Significant variation has also been found in all the stocks for duration of copulation between first and second matings. The duration of copulation is shorter in second mating as compared to first mating inD. ananassae.     

烟夜蛾性肽受体基因的克隆与表达模式分析

【目的】克隆烟夜蛾Helicoverpa assulta (Guenée)性肽受体基因并分析其表达模式, 为深入研究性肽与交配后反应的关系奠定基础。【方法】采用RT-PCR方法, 从烟夜蛾雌蛾性信息素腺体中得到性肽受体基因cDNA全序列。利用荧光定量PCR方法, 分析该基因的表达模式。【结果】序列分析结果显示, 烟夜蛾性肽受体基因cDNA全长2 048 bp, 命名为HassSPR（GenBank登录号: AFH53182.1）。该基因的开放阅读框长1 275 bp, 编码424个氨基酸残基, 序列中含有7个跨膜域结构, 预测分子量和等电点分别为48.6 kDa和9.25。序列比对分析表明, HassSPR与近缘种棉铃虫H. armigera和其他蛾类性肽受体的氨基酸序列一致性分别达98.35%和超过84%, 与已经报道的其他昆虫的性肽受体的氨基酸序列一致性也在64%以上。不同组织表达分析表明, HassSPR在测定的1日龄雌蛾不同组织中均有表达, 以在脑中的表达量最高。时序表达分析表明, 在羽化前1 天至羽化后6日龄雌蛾的信息素腺体中均有表达, 以3日龄表达量最高。雌蛾交配后, HassSPR在性信息素腺体和脑中的表达量显著上调, 而在交配囊和卵巢中的表达量显著下调。【结论】从烟夜蛾雌蛾性信息素腺体中克隆得到性肽受体基因HassSPR, 其表达模式提示该基因的表达水平与雌蛾的生殖生理和生殖行为有关。     

Using Doubly-Labeled Water to Measure Energy Expenditure in an Important Small Ectotherm Drosophila melanogaster

Energy expenditure is a key variable in the study of ageing,and the fruit fly Drosophila melanogaster is a model organism that has been used to make step changes in our understanding of the ageing process.Standard methods for measurement of energy expenditure involve placing individuals in metabolic chambers where their oxygen consumption and CO:production can be quantified.These measurements require separating individuals from any social context,and may only poorly reflect the environment in which the animals normally live.The doubly-labeled water(DLW) method is an isotope-based technique for measuring energy expenditure which overcomes these problems.However,technical challenges mean that the smallest animals this method has been previously applied to weighed 50-200 mg.We overcame these technical challenges to measure energy demands in Drosophila weighing 0.78 mg.Mass-specific energy expenditure varied between 43 and 65 raW-g.These estimates are considerably higher than estimates using indirect calorimetry of Drosophila in small metabolic chambers(around 18 mW-g).The methodology we have established extends downwards by three orders of magnitude the size of animals that can be measured using DLW.This approach may be of considerable value in future ageing research attempting to understand the genetic and genomic basis of ageing.     

活性肽P物质应用性研究

SP具有多种生理功能和作用,许多基础性的理论研究在国际上己进行了深入的研究,但是,SP在应用领域的报道是较少的。本文首先介绍了SP在医药方面的应用,旨在使SP变成一个生化药物即SP软膏(商品名为脑素软膏)。其次,在我们研究SP药用性质的同时,已注意到SP在化妆品方面的应用,如研究出SP高级营养霜;SP止痒宁露水;SP斑秃霜。第三,SP(猪脑)生化试剂的研究和制备,经由坂口试剂(精氨酸特征试剂)测定,可获得SP含量为30%或60%。     

Systematic screening of all signal peptides from Bacillus subtilis: a powerful strategy in optimizing heterologous protein secretion in Gram-positive bacteria

Efficient protein secretion is very important in biotechnology as it provides active and stable enzymes, which are an essential prerequisite for successful biocatalysis. Therefore, optimizing enzyme-producing bacterial strains is a major challenge in the field of biotechnology and protein production. In this study, the Gram-positive model bacterium Bacillus subtilis was optimized for heterologous protein secretion using a novel approach. Two lipolytic enzymes, cutinase from Fusarium solani pisi and a cytoplasmatic esterase of metagenomic origin, were chosen as reporters for heterologous protein secretion. In a systematic screening approach, all naturally occurring (non-lipoprotein) Sec-type signal peptides (SPs) from B. subtilis were characterized for their potential in heterologous protein secretion. Surprisingly, optimal SPs in cutinase secretion were inefficient in esterase secretion and vice versa, indicating the importance of an optimal fit between the SP and the respective mature part of the desired secretion target proteins. These results highlight the need for individually optimal signal peptides for every heterologous secretion target. Therefore, the SP library generated in this study represents a powerful tool for secretion optimization in Gram-positive expression hosts.