Origin and domestication of the fungal wheat pathogen Mycosphaerella graminicola via sympatric speciation

The Fertile Crescent represents the center of origin and earliest known place of domestication for many cereal crops. During the transition from wild grasses to domesticated cereals, many host-specialized pathogen species are thought to have emerged. A sister population of the wheat-adapted pathogen Mycosphaerella graminicola was identified on wild grasses collected in northwest Iran. Isolates of this wild grass pathogen from 5 locations in Iran were compared with 123 M. graminicola isolates from the Middle East, Europe, and North America. DNA sequencing revealed a close phylogenetic relationship between the pathogen populations. To reconstruct the evolutionary history of M. graminicola, we sequenced 6 nuclear loci encompassing 464 polymorphic sites. Coalescence analyses indicated a relatively recent origin of M. graminicola, coinciding with the known domestication of wheat in the Fertile Crescent around 8,000-9,000 BC. The sympatric divergence of populations was accompanied by strong genetic differentiation. At the present time, no genetic exchange occurs between pathogen populations on wheat and wild grasses although we found evidence that gene flow may have occurred since genetic differentiation of the populations.     

Substrate-induced double sided H-bond network as a means of domain closure in 3-phosphoglycerate kinase

Closure of the two domains of 3-phosphoglycerate kinase, upon substrate binding, is essential for the enzyme function. The available crystal structures cannot provide sufficient information about the mechanism of substrate assisted domain closure and about the requirement of only one or both substrates, since lattice forces may hinder the large scale domain movements. In this study the known X-ray data, obtained for the open and closed conformations, were probed by solution small-angle X-ray scattering experiments. The results prove that binding of both substrates is essential for domain closure. Molecular graphical analysis, indeed, reveals formation of a double-sided H-bond network, which affects substantially the shape of the main molecular hinge at beta-strand L, under the concerted action of both substrates.     

Systemic and mucosal antibody response in experimental Chlamydia pneumoniae infection of mice

Chlamydia pneumoniae is a common human respiratory pathogen, and sera from infected individuals recognize several proteins of C. pneumoniae. We produced C. pneumoniae-specific proteins in a Bacillus subtilis expression system. We then used these recombinant C. pneumoniae proteins and purified C. pneumoniae elementary bodies as antigens in enzyme immunoassays to assess the kinetics and protein specificity of the systemic and mucosal antibody responses induced by C. pneumoniae intranasal infection in BALB/c mice. The systemic antibodies in mice recognized strong 'key' immunogens of Chlamydia, Omp2 and Hsp60, but weakly targeted the MOMP protein, the major immunogen in chlamydial species other than C. pneumoniae. The IgA antibodies in bronchial secretions specifically recognized the putative surface protein of C. pneumoniae, Omp4. Our preliminary observations point to the necessity of further characterization of the mucosal antibody response during C. pneumoniae infection.     

Jellyfish and other cnidarian envenomations cause pain by affecting TRPV1 channels

Cnidarian envenomations cause a burning-pain sensation of which the underlying mechanisms are unknown. Activation of TRPV1, a non-selective cation channel expressed in nociceptive neurons, leads to cell depolarisation and pain. Here, we show in vitro and in vivo evidence for desensitization-dependent TRPV1 activation in cnidarian envenomations. Cnidarian venom induced a nociceptive reactivity, comparable to capsaicin, in laboratory rats, which could be reduced by the selective TRPV1 antagonist, BCTC. These findings are the first to explain at least part of the symptomology of cnidarian envenomations and provide insights into the design of more effective treatments for this global public health problem.     

Memory Consolidation in the Cerebellar Cortex

Several forms of learning, including classical conditioning of the eyeblink, depend upon the cerebellum. In examining mechanisms of eyeblink conditioning in rabbits, reversible inactivations of the control circuitry have begun to dissociate aspects of cerebellar cortical and nuclear function in memory consolidation. It was previously shown that post-training cerebellar cortical, but not nuclear, inactivations with the GABA_A agonist muscimol prevented consolidation but these findings left open the question as to how final memory storage was partitioned across cortical and nuclear levels. Memory consolidation might be essentially cortical and directly disturbed by actions of the muscimol, or it might be nuclear, and sensitive to the raised excitability of the nuclear neurons following the loss of cortical inhibition. To resolve this question, we simultaneously inactivated cerebellar cortical lobule HVI and the anterior interpositus nucleus of rabbits during the post-training period, so protecting the nuclei from disinhibitory effects of cortical inactivation. Consolidation was impaired by these simultaneous inactivations. Because direct application of muscimol to the nuclei alone has no impact upon consolidation, we can conclude that post-training, consolidation processes and memory storage for eyeblink conditioning have critical cerebellar cortical components. The findings are consistent with a recent model that suggests the distribution of learning-related plasticity across cortical and nuclear levels is task-dependent. There can be transfer to nuclear or brainstem levels for control of high-frequency responses but learning with lower frequency response components, such as in eyeblink conditioning, remains mainly dependent upon cortical memory storage.     

Primate models for human immunodeficiency virus infection. Evolution of receptor use during pathogenesis

Animal models greatly facilitate understanding of transmission, pathogenesis and immune responses in HIV and SIV infection and provide models for studies on the effect of candidate drugs or vaccines. However, there are several aspects that one should consider when drawing conclusions from results obtained from animal models. First, the genetic relationship of primate lentiviruses cannot be disregarded because it is known that HIV-1 is more closely related to SIV of chimpanzee origin (SIVcpz) than to SIV from sooty mangabey (SIVsm) origin. Nevertheless, SIVsm and SIVmac are the ones most often used as model systems. Second, there are differences in the biological properties, like CXCR4 use and CD4-independent coreceptor use, of HIV and SIV. These differences might be relevant in virus transmission, pathogenesis and in evoking immune responses. Third, in vivo and in vitro selection may influence the results. Neutralizing antibodies may play a role in selection of variant viruses since neutralization sensitive, CD4-independent SIVsm variants seemed to be suppressed in animals that mounted a neutralizing antibody response. It is tempting to speculate that neutralizing antibodies shape the SIV/HIV infection by selecting variants with a more "closed" envelope conformation with consequences for both receptor binding and neutralization sensitivity. The SIV/monkey model, although it has important advantages, may not answer all questions asked about HIV-1 infection in human.     

Lats2/Kpm is required for embryonic development, proliferation control and genomic integrity

The Drosophila melanogaster warts/lats tumour suppressor has two mammalian counterparts LATS1/Warts-1 and LATS2/Kpm. Here, we show that mammalian Lats orthologues exhibit distinct expression profiles according to germ cell layer origin. Lats2(-/-) embryos show overgrowth in restricted tissues of mesodermal lineage; however, lethality ultimately ensues on or before embryonic day 12.5 preceded by defective proliferation. Lats2(-/-) mouse embryonic fibroblasts (MEFs) acquire growth advantages and display a profound defect in contact inhibition of growth, yet exhibit defective cytokinesis. Lats2(-/-) embryos and MEFs display centrosome amplification and genomic instability. Lats2 localizes to centrosomes and overexpression of Lats2 suppresses centrosome overduplication induced in wild-type MEFs and reverses centrosome amplification inherent in Lats2(-/-) MEFs. These findings indicate an essential role of Lats2 in the integrity of processes that govern centrosome duplication, maintenance of mitotic fidelity and genomic stability.     

Electrophoretic behavior of the H+-ATPase proteolipid from bovine heart mitochondria

The proteolipid subunit of H⁺-ATPase was labeled by [¹⁴C]N,N-dicyclohexylcarbodiimide in bovine heart mitochondria. The radioactive labeling was followed using various systems of sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). When using discontinuous SDS-PAGE (Laemmli, U.K., 1970,Nature (London)227, 680–685) a monomeric (Mr 7600±1500) and a dimeric form (Mr 17,800±1200) of the proteolipid were detected, while only the monomeric form was found on urea (8 M) containing gels (SDS-PAGE according to Laemmli; or Swank, R. T., and Munkers, K. D., 1971,Anal. Biochem. 39, 462–477). When using SDS-PAGE with Na-P_i buffer (Weber, K., and Osborn, M., 1969,J. Biol. Chem. 244, 4406–4442), only a dimeric form of the proteolipid (Mr 15,000±1000) was detected. Experimental data indicate that the different patterns of proteolipid separation are related to the presence of the two distinct proteolipid conformations in the SDS solution.