Contrasting patterns of X‐chromosome divergence underlie multiple sex‐ratio polymorphisms in stalk‐eyed flies

Sex‐linked segregation distorters cause offspring sex ratios to differ from equality. Theory predicts that such selfish alleles may either go to fixation and cause extinction, reach a stable polymorphism or initiate an evolutionary arms race with genetic modifiers. The extent to which a sex ratio distorter follows any of these trajectories in nature is poorly known. Here, we used X‐linked sequence and simple tandem repeat data for three sympatric species of stalk‐eyed flies (Teleopsis whitei and two cryptic species of T. dalmanni) to infer the evolution of distorting X chromosomes. By screening large numbers of field and recently laboratory‐bred flies, we found no evidence of males with strongly female‐biased sex ratio phenotypes (SR) in one species but high frequencies of SR males in the other two species. In the two species with SR males, we find contrasting patterns of X‐chromosome evolution. T. dalmanni‐1 shows chromosome‐wide differences between sex‐ratio (X^SR) and standard (X^ST) X chromosomes consistent with a relatively old sex‐ratio haplotype based on evidence including genetic divergence, an inversion polymorphism and reduced recombination among X^SR chromosomes relative to X^ST chromosomes. In contrast, we found no evidence of genetic divergence on the X between males with female‐biased and nonbiased sex ratios in T. whitei. Taken with previous studies that found evidence of genetic suppression of sex ratio distortion in this clade, our results illustrate that sex ratio modification in these flies is undergoing recurrent evolution with diverse genomic consequences.     

From the beginning to the present state of molecular microbial pathogenesis—A tribute to Pascale Cossart

The universe of Molecular Microbial Pathogenesis is filled with many female and male stars. But there are two particularly bright shining supernovae-like stars: the late Stanley Falkow and the very lively and creative Pascale Cossart. These two outstanding luminaries, surrounded by numerous planets, do not only belong to different scientific generations but their splendor also comes from very different scientific concepts. Stanley Falkow, often referred to as the ‘Father of Molecular Microbial Pathogenesis’, made many groundbreaking contributions to this field by addressing almost all important bacterial pathogens. Pascale Cossart, who could be called in analogy the ‘Queen of Modern Molecular Microbial Pathogenesis’ by combining the Microbiology and Cell Biology, concentrates in her similarly impressive scientific work essentially on a single bacterial species which she studied and still studies in great depth: the facultative intracellular bacterial pathogen Listeria monocytogenes—and the vast majority of her most prominent publications deals with this pathogen in almost all facets. It is certainly not an exaggeration to say that she together with her co-workers and collaborators developed this model bacterium into a paradigm among the intracellular bacterial pathogens.     

河南省16个主栽小麦品种抗叶锈基因分析

为了明确河南省小麦品种的抗叶锈性及抗叶锈基因的分布,为小麦品种推广与合理布局、叶锈病防治及抗病育种提供依据,本研究利用2015年采自河南省的5个小麦叶锈菌流行小种混合菌株,对近几年河南省16个主栽小麦品种进行了苗期抗性鉴定,然后选用12个小麦叶锈菌生理小种对这些品种进行苗期基因推导,同时利用与24个小麦抗叶锈基因紧密连锁(或共分离)的30个分子标记对该16个品种进行了抗叶锈基因分子检测。结果显示,供试品种苗期对小麦叶锈菌混合流行小种均表现高度感病;基因推导与分子检测结果表明,供试品种可能含有Lr1、Lr16、Lr26和Lr30这4个抗叶锈基因,其中先麦8号含有Lr1和Lr26;郑麦366和郑麦9023含有Lr1;西农979和怀川916含有Lr16;中麦895、偃展4110、郑麦7698、平安8号、众麦1号、周麦16、衡观35和矮抗58含有Lr26;周麦22中含有Lr26,还可能含有Lr1和Lr30;豫麦49-198和洛麦23可能含有本研究中检测以外的其他抗叶锈基因。因此,河南省主栽小麦品种的抗叶锈基因丰富度较低,今后育种工作应注重引入其他抗叶锈性基因,提高抗叶锈性,有效控制小麦叶锈病。     

Isolation and characterization of cDNA clones for RNA species induced by substituted benzenesulfonamides in corn

A search of compounds capable of inducing specific gene expression in plants without affecting growth and development led to the examination of changes in the pattern of gene expression in corn after treatment with substituted benzenesulfonamide herbicide safeners. Following hydroponic treatment of corn with the safener N-(aminocarbonyl)-2-chlorobenzenesulfonamide (2-CBSU), the specific induction of new translatable mRNA species was observed. Replicate copies of a cDNA library made using RNA from 2-CBSU-treated corn roots were differentially screened with cDNA probes made from either the same mRNA fraction used for library construction or mRNA isolated from roots treated with 2-chlorobenzenesulfonamide (2-CBSA), an inactive analog of the safener. Colonies showing hybridization only with the probe made using mRNA from 2-CBSU-treated roots were further characterized to assess the specificity of the induction and decay of the corresponding induced RNA species. RNA blot analyses showed two clones, designated In2-1 and In2-2, contained plasmids that hybridized to RNAs that were induced from an undetectable background in corn roots within 30 minutes after treatment with 2-CBSU. Leaf and meristem tissues showed similar inductions of the In2-1 and In2-2 RNA species after a delay of several hours. In addition, both RNA species were induced in corn by foliar application of 2-CBSU. In contrast, neither RNA species was induced following stress treatments of plants. These results indicate a substituted benzenesulfonamide safener might be used with the promoters from the In2-1 and In2-2 genes to develop a new inducible gene expression system for plants.     

The evolution of early vertebrate photoreceptors

Meeting the challenge of sampling an ancient aquatic landscape by the early vertebrates was crucial to their survival and would establish a retinal bauplan to be used by all subsequent vertebrate descendents. Image-forming eyes were under tremendous selection pressure and the ability to identify suitable prey and detect potential predators was thought to be one of the major drivers of speciation in the Early Cambrian. Based on the fossil record, we know that hagfishes, lampreys, holocephalans, elasmobranchs and lungfishes occupy critical stages in vertebrate evolution, having remained relatively unchanged over hundreds of millions of years. Now using extant representatives of these ‘living fossils’, we are able to piece together the evolution of vertebrate photoreception. While photoreception in hagfishes appears to be based on light detection and controlling circadian rhythms, rather than image formation, the photoreceptors of lampreys fall into five distinct classes and represent a critical stage in the dichotomy of rods and cones. At least four types of retinal cones sample the visual environment in lampreys mediating photopic (and potentially colour) vision, a sampling strategy retained by lungfishes, some modern teleosts, reptiles and birds. Trichromacy is retained in cartilaginous fishes (at least in batoids and holocephalans), where it is predicted that true scotopic (dim light) vision evolved in the common ancestor of all living gnathostomes. The capacity to discriminate colour and balance the tradeoff between resolution and sensitivity in the early vertebrates was an important driver of eye evolution, where many of the ocular features evolved were retained as vertebrates progressed on to land.     

A testis‐specific gene within a widely expressed gene: Contrasting evolutionary patterns of two differentially expressed mammalian proteins encoded by a single gene,CAMK4

Understanding the patterns of genetic variations within fertility‐related genes and the evolutionary forces that shape such variations is crucial in predicting the fitness landscapes of subsequent generations. This study reports distinct evolutionary features of two differentially expressed mammalian proteins [CaMKIV (Ca²⁺/calmodulin‐dependent protein kinase IV) and CaS (calspermin)] that are encoded by a single gene, CAMK4. The multifunctional CaMKIV, which is expressed in multiple tissues including testis and ovary, is evolving at a relatively low rate (0.46–0.64 × 10^?9 nucleotide substitutions/site/year), whereas the testis‐specific CaS gene, which is predominantly expressed in post‐meiotic cells, evolves at least three to four times faster (1.48–1.98 × 10^?9 substitutions/site/year). Concomitantly, maximum‐likelihood‐based selection analyses revealed that the ubiquitously expressed CaMKIV is constrained by intense purifying selection and, therefore, remained functionally highly conserved throughout the mammalian evolution, whereas the testis‐specific CaS gene is under strong positive selection. The substitution rates of different mammalian lineages within both genes are positively correlated with GC content, indicating the possible influence of GC‐biased gene conversion on the estimated substitution rates. The observation of such unusually high GC content of the CaS gene (≈74%), particularly in the lineage that comprises the bovine species, suggests the possible role of GC‐biased gene conversion in the evolution of CaS that mimics positive selection.     

Type I interferon genes in cattle: restriction fragment length polymorphisms,gene numbers and physical organization on bovine chromosome 8

Multiple, superimposed Type I interferon (IFN) restriction fragments were resolved following 72–92 h of horizontal electrophoresis. Restriction fragment length polymorphisms (RFLPs) for α IFN (IFNA), β IFN (IFNB), ωIFN (IFNW) and trophoblast IFN (IFNT) genes were identified in Hin dill, Eco RI and Taql digestions from 313 cattle. RFLPs with codominant segregation in cattle pedigrees were considered alleles, and 19 distinct polymorphic Type I IFN loci (5 IFNA, 4 IFNB, 8 IFNW and 2 IFNT) were identified. Allele frequencies and observed heterozygosity values were calculated for each locus and several loci were considered highly informative for linkage analysis. Bovine IFN gene numbers (10 IFNA, 6 IFNB, 20 IFNW and 6 IFNT) were estimated from the number of polymorphic loci plus additional monomorphic hybridizing bands present in Eco RI and Hindlll digestions. Physical linkage of the Type I IFN gene families on bovine chromosome 8 was demonstrated by pulsed field gel electrophoresis (PFGE). Hybridization of two or more IFN probes to similarly sized PFGE fragments suggested the tentative gene family order: IFNA/IFNW-IFNT-IFNB. These studies provide a basis for the development of more detailed genetic and physical maps of the bovine Type I IFNs.