Molecular detection of Wolbachia pipientis in natural populations of sandfly vectors of Leishmania infantum in endemic areas: first detection in Lutzomyia longipalpis

A polymerase chain reaction‐based method was used to screen sandflies for infection with Wolbachia (Rickettsiales: Rickettsiaceae), an intracellular bacterial endosymbiont found in many arthropods and filarial hosts. Positive results were obtained in five of 200 field‐collected sandflies and were confirmed by sequencing. All sandflies were Lutzomyia longipalpis (Diptera: Psychodidae) captured in a region endemic for visceral leishmaniasis in Brazil. This is the first study to identify Wolbachia infection in this Lutzomyia species, which is the main vector of leishmaniasis in the study area. The low infection rate found in this study (2.5%), together with the lack of detection of Wolbachia in previous studies and the diversity found in the sequences analysed, suggests horizontal transmission to these sandflies.     

Do chromosomal hybrids necessarily suffer from developmental instability?

The role of chromosomal rearrangements in disturbing reproduction in hybrids between karyotypically differentiated groups is fairly well documented. However, the effect of chromosomal changes at other phenotypic levels is rarely considered. In Tunisia, natural chromosomal hybrids of the house mouse exhibit developmental instability, suggesting that a high karyotypic heterozygosity might also affect developmental processes. If this is true, we predict that, in this species, developmental instability should arise in hybrids between any populations with a high chromosomal differentiation. To test this hypothesis, we compare the results obtained in Tunisian mice with those obtained in the present analysis on Madeiran mice. Both systems of races have similar levels of chromosomal differentiation (nine Robertsonian fusions). Unlike Tunisian mice, hybrids in Madeira display a similar level of developmental instability as parental groups. This indicates that structural heterozygosity per se does not necessarily impair developmental stability. It further suggests that chromosomal fusions are not all equivalent in their phenotypic effects, and that the identity of each fusion should be taken into account.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 33–43.     

中国‘苦水’玫瑰杂交育性的初步研究

油用玫瑰主栽品种‘苦水’玫瑰的栽培园区总见千花无果现象,为此,本研究对‘苦水’玫瑰的杂交育性进行了遗传学研究。授粉试验发现,自然授粉和人工辅助授粉时‘苦水’玫瑰自交不结实;异交时,‘苦水’玫瑰作为母本与‘丰花’玫瑰、‘四季’玫瑰、‘艳霞’玫瑰、重瓣黄刺玫之间具有亲和性,而作为父本与杂交母本都无法成功授粉结实。在雄蕊花瓣化、P/O值、花粉异型性和花粉萌发率等生殖特征中发现‘苦水’玫瑰的花粉畸形现象严重,萌发率近似为零。进而,显微观察小孢子母细胞减数分裂各时相发现‘苦水’玫瑰中存在染色体分配行为不协调,胞质分裂不均一,四分体中有三分体等异常现象。由此可见‘苦水’玫瑰的异常减数分裂行为致花粉败育妨碍其做父本时的受精结实,故雄性不育而非蔷薇科常见的自交不亲和性,是‘苦水’玫瑰自交不结实的主要原因,也表明作为母本通过杂交育种方法改良‘苦水’玫瑰的种质是可行的。     

Does the disturbance hypothesis explain the biomass increase in basin‐wide Amazon forest plot data?

Positive aboveground biomass trends have been reported from old-growth forests across the Amazon basin and hypothesized to reflect a large-scale response to exterior forcing. The result could, however, be an artefact due to a sampling bias induced by the nature of forest growth dynamics. Here, we characterize statistically the disturbance process in Amazon old-growth forests as recorded in 135 forest plots of the RAINFOR network up to 2006, and other independent research programmes, and explore the consequences of sampling artefacts using a data-based stochastic simulator. Over the observed range of annual aboveground biomass losses, standard statistical tests show that the distribution of biomass losses through mortality follow an exponential or near-identical Weibull probability distribution and not a power law as assumed by others. The simulator was parameterized using both an exponential disturbance probability distribution as well as a mixed exponential–power law distribution to account for potential large-scale blowdown events. In both cases, sampling biases turn out to be too small to explain the gains detected by the extended RAINFOR plot network. This result lends further support to the notion that currently observed biomass gains for intact forests across the Amazon are actually occurring over large scales at the current time, presumably as a response to climate change.     

STUDIES ON THE FORMATION AND STATE OF DETERMINATION OF THE TRUNK ORGANIZER IN THE NEWT, CYNOPS PYRRHOGASTER

Mesoderm formation in the presumptive trunk organizer was analyzed in gastrulae of Cynops pyrrhogaster. The presumptive trunk organizer showed little or no mesodermal differentiation in the beginning gastrula (0 h embryo). But as soon as the presumptive trunk organizer came into contact with the newly invaginated cranial archenteron roof, it rapidly formed mesoderm. This suggests that this differentiation was brought about by an inductive effect of the underlying cranial archenteron roof. For investigation of this possibility, the presumptive trunk organizer of 0 h embryos (Tr-0) and the newly invaginated cranial archenteron roof (presumptive pharyngeal endoderm and prechordal plate) of successive stages were cultured in isolation and by the sandwich technique. The newly invaginated presumptive pharyngeal endoderm and prechordal plate had no effect on mesoderm formation of the presumptive trunk organizer, and mesodermal differentiation of the combinations was similar to that of the Tr-0 alone. On the other hand, results showed that the prechordal plate, which came into contact with the still uninvaginated presumptive trunk organizer, stimulated dorsalisation of the weakly mesodermized trunk organizer. Based on these results, the stepwise process of mesoderm formation in the trunk organizer is discussed.     

Reproductive system and fitness of Vriesea friburgensis,a self‐sterile bromeliad species

Reproductive biology and plant fertility are directly related to many aspects of plant evolution and conservation biology. Vriesea friburgensis is an epiphytic and terrestrial bromeliad endemic to the Brazilian Atlantic rainforest. Hand‐pollination experiments were used to examine the reproductive system in a wild population of V. friburgensis. Plant fertility was assigned considering flower production, fruit and seed set, seed germination, and pollen viability. Self‐sterility observed from spontaneous selfing and manual self‐pollination treatments may be the consequence of late‐acting self‐incompatibility. Hand‐pollination results indicated no pollen limitation in the population studied. Floral biology features such as a few daily open flowers, nectar production, and sugar concentration corroborate hummingbirds as effective pollinators, although bees were also documented as pollinators. Components of fitness such as high flower, fruit, and seed production together with high seed and pollen viability indicate that this wild population is viable. From a conservation point of view, we highlight that this self‐sterile species depends on pollinator services to maintain its population fitness and viability through cross‐pollination. Currently, pollinators are not limited in this population of V. friburgensis. Conversely, the maintenance and continuous conservation of this community is essential for preserving this plant–pollinator mutualism.     

反义锁核酸阻断耐甲氧西林金黄色葡萄球菌agr群体感应系统

目的:利用反义策略,设计、筛选针对agrA mRNA的反义锁核酸,阻断agr群体感应系统,降低MRSA毒力因子的表达,减小细菌生存压力,为抗耐药菌感染提供一种新策略。方法:应用Primer Premier 5.0和RNA structure 4.5两种软件,设计、筛选2条针对agrA mRNA的反义寡核苷酸序列,对其进行锁核酸修饰,并与透膜肽(KFF)3K共价连接,将这两条反义序列导入细菌体内。体外与MRSA共培养,观察细菌生存情况。实时定量PCR检测其对agrA及agr群体感受系统的效应分子RNAⅢ和下游毒力基因hla的转录水平的影响,Western blot检测其是否能抑制α-溶血素的表达。结果:两条反义锁核酸序列PLNA34和PLNA522在体外均无抗菌活性,但都能不同程度的抑制agrA,RNAⅢ和hla的转录水平;相比较而言,PLNA34的抑制效果更佳,并能明显抑制α-溶血素的分泌表达。结论:agrA可作为抗MRSA感染的新靶点,为新型抗MRSA药物的研发提供了理论基础。