Relationships among tetraploid wheat (Triticum turgidum L.) landrace populations revealed by isozyme markers and agronomic traits

Diversity and relationships among ten tetraploid wheat landrace populations, collected from different localities in the central highlands of Ethiopia, were studied using isozyme markers and agronomic traits. This type of analysis in crop species is fundamental for designing optimal germ plasm collection, management practices and for developing an index for parental selection. The populations differed in allelic frequencies. Gene-diversity estimates showed that the populations encompass an appreciable amount of variation. However, differentiation between them was low, as was also confirmed by the presence of gene flow. Much of the diversity (85%), was attributable to the within-population level. The genetic distances were mostly small with the exception of those between a few pairs of populations. Thus, the relationships discerned among the populations were more of a similarity nature which could be ascribed to sharing a common ancestral population and/or adaptation to similar climatic conditions. The pattern of genetic divergence appeared to be independent of geographic distance. Considerable divergence in the agronomic traits was observed for certain populations. Cluster analyses of the isozyme and agronomic data produced different patterns and memberships of groupings. This lack of agreement could be ascribed to the different forces of evolution acting on isozyme markers and agronomic traits since agronomic traits, are the prime target of artificial selection. The clustering based on agronomic traits resulted in grouping together populations with similar agronomic performance. The results of this study suggest that taking more samples within a locality or population would be a better approach to capture the range of variation in the landrace populations of the central highlands of Ethiopia.     

Quantitative trait loci controlling light and hormone response in two accessions of Arabidopsis thaliana

We have mapped quantitative trait loci (QTL) responsible for natural variation in light and hormone response between the Cape Verde Islands (Cvi) and Landsberg erecta (Ler) accessions of Arabidopsis thaliana using recombinant inbred lines (RILs). Hypocotyl length was measured in four light environments: white, blue, red, and far-red light and in the dark. In addition, white light plus gibberellin (GA) and dark plus the brassinosteroid biosynthesis inhibitor brassinazole (BRZ) were used to detect hormone effects. Twelve QTL were identified that map to loci not previously known to affect light response, as well as loci where candidate genes have been identified from known mutations. Some QTL act in all environments while others show genotype-by-environment interaction. A global threshold was established to identify a significant epistatic interaction between two loci that have few main effects of their own. LIGHT1, a major QTL, has been confirmed in a near isogenic line (NIL) and maps to a new locus with effects in all light environments. The erecta mutation can explain the effect of the HYP2 QTL in the blue, BRZ, and dark environments, but not in far-red. LIGHT2, also confirmed in an NIL, has effects in white and red light and shows interaction with GA. The phenotype and map position of LIGHT2 suggest the photoreceptor PHYB as a candidate gene. Natural variation in light and hormone response thus defines both new genes and known genes that control light response in wild accessions.     

Synthesis and structure-activity relationships of M(2)-selective muscarinic receptor ligands in the 1-[4-(4-arylsulfonyl)-phenylmethyl]-4-(4-piperidinyl)-piperazine family

The synthesis and muscarinic binding properties of compounds based on the 1-[4-(4-arylsulfonyl)phenylmethyl]-4-(1-aroyl-4-piperidinyl)-piperazine skeleton are described. For compounds, substituted with appropriately configured methyl groups at the benzylic center and at the piperazine 2-position, high levels of selective, M(2) subtype affinity could be obtained, particularly when the terminal N-aroyl residue was ortho-substituted.     

Increased cell division but not thymic dysfunction rapidly affects the T-cell receptor excision circle content of the naive T cell population in HIV-1 infection

Recent thymic emigrants can be identified by T cell receptor excision circles (TRECs) formed during T-cell receptor rearrangement. Decreasing numbers of TRECs have been observed with aging and in human immunodeficiency virus (HIV)-1 infected individuals, suggesting thymic impairment. Here, we show that in healthy individuals, declining thymic output will affect the TREC content only when accompanied by naive T-cell division. The rapid decline in TRECs observed during HIV-1 infection and the increase following HAART are better explained not by thymic impairment, but by changes in peripheral T-cell division rates. Our data indicate that TREC content in healthy individuals is only indirectly related to thymic output, and in HIV-1 infection is mainly affected by immune activation.     

Tetracyclic sulfones as potent γ-secretase inhibitors: Synthesis and structure–activity relationship studies

Complex tetracyclic sulfones were designed as γ-secretase inhibitors and a stereoselective synthesis was achieved. γ-Secretase activity was seen predominately in the (?) enantiomeric series. Compounds such as 2a and 2b showed remarkable in vitro and in vivo potency.     

Small conformationally restricted piperidine N-arylsulfonamides as orally active gamma-secretase inhibitors

The design and development of a new class of small 2,6-disubstituted piperidine N-arylsulfonamide gamma-secretase inhibitors is reported. Lowering molecular weight including the use of conformational constraint led to compounds with less CYP 3A4 liability compared to early leads. Compounds active orally in lowering Abeta levels in Tg CRND8 mice were identified as potential treatments for Alzheimer's disease.     

Requirement of homeobox gene STIMPY/WOX9 for Arabidopsis meristem growth and maintenance

Most organs of flowering plants develop postembryonically from groups of pluripotent cells called meristems [1]. The shoot apical meristem (SAM) is specified by two complementary pathways [2-4]. SHOOT MERISTEMLESS (STM; [5]) defines the entire SAM region [6]. WUSCHEL (WUS), on the other hand, functions in a more restricted set of cells to promote stem-cell fate and is regulated by the CLAVATA genes in a negative feedback loop [7-10]. In contrast, little is known about how the growth of the SAM, which increases in size during vegetative development [11], is regulated. We have characterized STIMPY (STIP; also called WOX9 [12]), a homeobox gene required for the growth of the vegetative SAM, in part by positively regulating WUS expression. In addition, STIP is required in several other aerial organs and the root. What sets STIP apart from STM and WUS is that stip mutants can be fully rescued by stimulating the entry into the cell cycle with sucrose. Therefore, STIP is likely to act in all these tissues by maintaining cell division and preventing premature differentiation. Taken together, our findings suggest that STIP identifies a new genetic pathway integrating developmental signals with cell-cycle control.     

Factors Associated with Leishmania Asymptomatic Infection: Results from a Cross-Sectional Survey in Highland Northern Ethiopia

Background

In northern Ethiopia the prevalence of visceral leishmaniasis is steadily rising posing an increasing public health concern. In order to develop effective control strategies on the transmission of the disease it is important to generate knowledge on the epidemiological determinants of the infection.

Methodology/Principal Findings

We conducted a cross-sectional survey on children 4–15 years of age using a multi staged stratified cluster sampling on high incidence sub-districts of Amhara regional state, Ethiopia. The survey included a socio-demographic, health and dietary questionnaire, and anthropometric measurements. We performed rK39-ICT and DAT serological tests in order to detect anti-Leishmania antibodies and carried out Leishmanin Skin Test (LST) using L.major antigen. Logistic regression models were used. Of the 565 children surveyed 56 children were positive to infection (9.9%). The individual variables that showed a positive association with infection were increasing age, being male and sleeping outside [adjusted odds ratios (95% CI): 1.15 (1.03, 1.29), 2.56 (1.19, 5.48) and 2.21 (1.03, 4.71) respectively] and in relation to the household: past history of VL in the family, living in a straw roofed house and if the family owned sheep [adjusted OR (95% CI): 2.92 (1.25, 6.81), 2.71 (1.21, 6.07) and 4.16 (1.41, 12.31) respectively].

Conclusions/Significance

A behavioural pattern like sleeping outside is determinant in the transmission of the infection in this area. Protective measures should be implemented against this identified risk activity. Results also suggest a geographical clustering and a household focalization of the infection. The behaviour of the vector in the area needs to be clarified in order to establish the role of domestic animals and house materials in the transmission of the infection.