乙醛磺酸对小鼠胚胎细胞遗传和胚胎发育影响的研究

本文报道乙醛磺酸（ＳＡＤ）不仅会降低小鼠胚胎细胞的ｒＲＮＡ基因转录活性,而且还明显提高了胚胎细胞姐妹染色单体互换（ＳＣＥ）频率,导致胚胎发育停滞和胎儿死亡,最终使幼鼠出生率明显下降。当ＳＡＤ浓度为１０－５ｍｏｌ／Ｌ时,小鼠胚胎细胞ｒＲＮＡ基因转录活性降低为正常值的１５％,并引起ＳＣＥ频率成倍增加,幼鼠出生率仅为正常值的５０％;当ＳＡＤ浓度增至１０－３ｍｏｌ／Ｌ时,此时ｒＲＮＡ基因转录活性完全被抑制,而且ＳＣＥ频率增加为正常值的４．８倍,幼鼠出生率从正常值１００％降为４％。ＳＡＤ对小鼠胚胎细胞这种细胞遗传学效应和对胚胎发育影响的程度与该药浓度成正相关。此外,我们还对ｒＲＮＡ基因转录活性和ＳＣＥ的改变与哺乳类胚胎发育之间的关系进行了初步的讨论。     

Deep sequencing reveals extensive variation in the gut microbiota of wild mosquitoes from Kenya

The mosquito midgut is a hostile environment that vector‐borne parasites must survive to be transmitted. Commensal bacteria in the midgut can reduce the ability of mosquitoes to transmit disease, either by having direct anti‐parasite effects or by stimulating basal immune responses of the insect host. As different bacteria have different effects on parasite development, the composition of the bacterial community in the mosquito gut is likely to affect the probability of disease transmission. We investigated the diversity of mosquito gut bacteria in the field using 454 pyrosequencing of 16S rRNA to build up a comprehensive picture of the diversity of gut bacteria in eight mosquito species in this population. We found that mosquito gut typically has a very simple gut microbiota that is dominated by a single bacterial taxon. Although different mosquito species share remarkably similar gut bacteria, individuals in a population are extremely variable and can have little overlap in the bacterial taxa present in their guts. This may be an important factor in causing differences in disease transmission rates within mosquito populations.     

Genetic Map of Diploid Wheat, Triticum Monococcum L., and Its Comparison with Maps of Hordeum Vulgare L

A genetic map of diploid wheat, Triticum monococcum L., involving 335 markers, including RFLP DNA markers, isozymes, seed storage proteins, rRNA, and morphological loci, is reported. T. monococcum and barley linkage groups are remarkably conserved. They differ by a reciprocal translocation involving the long arms of chromosomes 4 and 5, and paracentric inversions in the long arm of chromosomes 1 and 4; the latter is in a segment of chromosome arm 4L translocated to 5L in T. monococcum. The order of the markers in the inverted segments in the T. monococcum genome is the same as in the B and D genomes of T. aestivum L. The T. monococcum map differs from the barley maps in the distribution of recombination within chromosomes. The major 5S rRNA loci were mapped on the short arms of T. monococcum chromosomes 1 and 5 and the long arms of barley chromosomes 2 and 3. Since these chromosome arms are colinear, the major 5S rRNA loci must be subjected to positional changes in the evolving Triticeae genome that do not perturb chromosome colinearity. The positional changes of the major 5S rRNA loci in Triticeae genomes are analogous to those of the 18S-5.8S-26S rRNA loci.     

Inferring malaria parasite population structure from serological networks

The malaria parasite Plasmodium falciparum is characterized by high levels of genetic diversity at antigenic loci involved in virulence and immune evasion. Knowledge of the population structure and dynamics of these genes is important for designing control programmes and understanding the acquisition of immunity to malaria; however, high rates of homologous and non-homologous recombination as well as complex patterns of expression within hosts have hindered attempts to elucidate these structures experimentally. Here, we analyse serological data from Kenya using a novel network technique to deconstruct the relationships between patients' immune responses to different parasite isolates. We show that particular population structures and expression patterns produce distinctive signatures within serological networks of parasite recognition, which can be used to discriminate between competing hypotheses regarding the organization of these genes. Our analysis suggests that different levels of immune selection occur within different groups of the same multigene family leading to mixed population structures.     

The effect of host heterogeneity and parasite intragenomic interactions on parasite population structure

Understanding the processes that shape the genetic structure of parasite populations and the functional consequences of different parasite genotypes is critical for our ability to predict how an infection can spread through a host population and for the design of effective vaccines to combat infection and disease. Here, we examine how the genetic structure of parasite populations responds to host genetic heterogeneity. We consider the well-characterized molecular specificity of major histocompatibility complex binding of antigenic peptides to derive deterministic and stochastic models. We use these models to ask, firstly, what conditions favour the evolution of generalist parasite genotypes versus specialist parasite genotypes? Secondly, can parasite genotypes coexist in a population? We find that intragenomic interactions between parasite loci encoding antigenic peptides are pivotal in determining the outcome of evolution. Where parasite loci interact synergistically (i.e. the recognition of additional antigenic peptides has a disproportionately large effect on parasite fitness), generalist parasite genotypes are favoured. Where parasite loci act multiplicatively (have independent effects on fitness) or antagonistically (have diminishing effects on parasite fitness), specialist parasite genotypes are favoured. A key finding is that polymorphism is not stable and that, with respect to functionally important antigenic peptides, parasite populations are dominated by a single genotype.