Recent demographic histories of temperate deciduous trees inferred from microsatellite markers

Background Accurate inference of demographic histories for temperate tree species can aid our understanding of current climate change as a driver of evolution. Microsatellites are more suitable for inferring recent historical events due to their high mutation rates. However, most programs analyzing microsatellite data assume a strict stepwise mutation model (SMM), which could cause false detection of population shrinkage when microsatellite mutation does not follow SMM. Results This study aims to reconstruct the recent demographic histories of five cool-temperate tree species in Eastern Asia, Quercus mongolica, Q. liaotungensis, Juglans cathayensis, J. mandshurica and J. ailantifolia, by using 19 microsatellite markers with two methods considering generalized stepwise mutation model (GSM) (MIGRAINE and VarEff). Both programs revealed that all the five species experienced expansions after the Last Glacial Maximum (LGM). Within butternuts, J. cathayensis experienced a more serious bottleneck than the other species, and within oaks, Q. mongolica showed a moderate increase in population size and remained stable after the expansion. In addition, the point estimates of the multistep mutation proportion in the GSM model (pGSM) for all five species were between 0.50 and 0.65, indicating that when inferring population demographic history of the cool-temperate forest species using microsatellite markers, it is better to assume a GSM rather than a SMM. Conclusions This study provides the first direct evidence that five cool-temperate tree species in East Asia have experienced expansions after the LGM with microsatellite data. Considering the mutation model of microsatellite has a vital influence on demographic inference, combining multiple programs such as MIGRAINE and VarEff can effectively reduce errors caused by inappropriate model selection and prior setting.

Allelic polymorphism of microsatelite DNA locі of egg chikens

The analysis of allelic polymorphism of five industrial egg crosses of chickens by five microsatellite DNA loci (ADL0268, MCW216, LEI0094, ADL0278, and MCW248) was carried out. DNA loci were chosen according to the recommendations of the International Society for Animal Genetics (ISAG). Based on the results of mathematical-statistical processing and data analysis, the spectra and frequencies of allelic variability, the peculiarities of allele pools, were identified, and unique alleles were identified. In general, the species Gallus gallus is characterized by a specific character of allelic spectra for all investigated microsatellite DNA loci (P <0.001). The highest rates of allelic variability were recorded in brown crosses "Lohmann brown" and "Hisex brown" (Na (LimNa)=(9.2 (5-17) and 7.4 (6-11), respectively). The studied crosses were characterized by a shift in allelic spectra towards a decrease in the fragment length. “Lohmann white” stands out among the birds of other crosses by high consolidation for individual alleles for all studied microsatellites (from ADL278114 – 0.343 and ADL268108 – 0.485 to LEI094259 – 0.720, MCW0248213 – 0.785 and MCW0216137 – 0.920). Unique alleles with the highest frequency were found in brown cross chickens, and in the “Hy-Line W-98” bird, they were not found. The number of unique alleles identified varied from 1 ("Hisex white") to 11 ("Lohmann brown"). Locus LEI094 turned out to be the most polymorphic in terms of the number of unique alleles – 10 such allelic variants were identified for it. No unique alleles were identified at the ADL0268 locus. The obtained estimates criterion χ2 of K. Pearson indicate significant differences in the frequency distribution of alleles for all studied loci. When using the MICROSATELLITE ANALYSER software, it was found that the nature of the variability of the studied microsatellite DNA loci in five industrial crosses of the egg chickens, both in the number of identified alleles and in the nature of their distribution, corresponded to the stepwise mutation model (SMM).

Recent demographic histories of temperate deciduous trees inferred from microsatellite markers

Background Accurate inference of demographic histories of temperate tree species can aid our understanding of current climate change as a driver of evolution. Microsatellites are more suitable for reflecting recent historical events due to their high mutation rates. However, most programs analyze microsatellite data following a strict stepwise mutation model (SMM), which could cause false detection of population shrinkage when microsatellite mutation is not according with SMM. Results This study aims to reconstruct the recent demographic histories of five cool-temperate tree species, Quercus mongolica, Q. liaotungensis, Juglans cathayensis, J. mandshurica and J. ailantifolia, in eastern Asia by using 19 microsatellite markers and two methods considering generalized stepwise mutation model (GSM) (MIGRAINE and VarEff). Both types of software revealed that all populations experienced expansions after the Last Glacial Maximum (LGM). In particular, J. cathayensis experienced a more serious bottleneck in its history than the other species, leading to a smaller effective population of ancestors, while Q. mongolica showed only a moderate increase in population size and remained stable after the expansion. In addition, the point estimates of the multistep mutation proportion in the generalized stepwise mutation model (pGSM) in all populations were between 0.50 and 0.65, which indicates that when inferring population demographic history of the above forest species using microsatellite molecular markers, it is better to assume a GSM rather than a SMM. Conclusions This study provides the first direct evidence that five cool-temperate tree species in East Asia have experienced expansions after the LGM using microsatellites data. Moreover, since the mutation model of microsatellite have a vital influence on demographic inference, combining multiple software programs such as MIGRAINE and VarEff can effectively reduce unnecessary errors caused by inappropriate model selection and prior setting.

The origins of molecular diversity

At its simplest, evolution is change in the relative abundance of alternative alleles, from one generation to the next. But where do these different alleles come from? As the ultimate origin of all genetic novelty, the input of new mutations into a population forms the critical first step for incorporating biological detail into how we conceive of genome evolution. Chapter 2, “The origins of molecular diversity,” summarizes the many mechanisms of mutation, the distribution of fitness effects, and how to characterize mutational processes themselves in conceptual models. It covers point mutations, indels, microsatellites, transposable elements, and other mutation types in the context of the genetic code and gene duplication, as well as the role of mutation accumulation experiments in understanding mutation rates and fitness effects. The infinite alleles, infinite sites, and stepwise mutation models are summarized, along with the concept of homoplasy and complexities to the mutation process in nature. These important extra pieces of biological realism connect more closely the mechanisms of evolution to show the path toward a deeper analysis of genomes.

Variabilidade genética de larvas e alevinos de piracanjuba (Brycon orbignyanus)

RESUMO O objetivo do presente trabalho foi avaliar a variabilidade genética de larvas e alevinos de piracanjuba em programa de repovoamento. Foram coletadas 180 larvas de piracanjuba de três dias e 90 alevinos de três meses de idade. Foram avaliados cinco loci microssatélites, os quais produziram 19 alelos. Não houve presença de alelos raros nem perdas de alelos ao longo do período. A heterozigosidade observada foi superior nas larvas em relação aos alevinos. Houve desvio no equilíbrio de Hardy-Weinberg na maioria dos loci em ambos os grupos. O coeficiente de endogamia foi positivo em ambos os grupos, sendo a média dos alevinos superior em relação às larvas. O excesso de heterozigotos foi significativo no modelo Stepwise Mutation Model para os alevinos, indicando a possibilidade de efeito gargalo recente. Conclui-se que, apesar da adequada variabilidade genética encontrada, os valores do coeficiente de endogamia e a possibilidade de efeito gargalo nos alevinos atentam para a necessidade de constante monitoramento genético desses estoques antes da liberação no ambiente.

Genetic diversity of long-established populations of Elaeis guineensis jacquin (Arecaceae)

This study aimed to estimate the genetic diversity of three Elaeis guineensis populations in Rio Grande do Norte state, as well as to verify the decreases in effective population size. The population with the highest polymorphism was MAT (Mata) with+ 57 loci (72%), followed by RIA (Riacho) with 54 loci (68%) and HOR (Horta) with 34 loci (43.03%). The RIA population was shown to be the most genetically diverse, with Nei (h = 0.28) and Shannon (I = 0.41) diversity indices. There was high genetic differentiation among populations (AMOVA, analysis of molecular variance = 42%), which was separated into three distinct genetic groups according to a Bayesian analysis. There was a significant population decrease (P < 0.05) for the HOR population in the IAM (infinite allele model) and SMM (stepwise mutation model), and for the RIA population in the IAM. The data obtained in this study may support ex-situ conservation projects for Elaeis guineensis, contributing to the selection of genotypes and their sustainable use.

Amino Acid Substitution in the Major Multidrug Efflux Transporter Protein AcrB Contributes to Low Susceptibility to Azithromycin in Haemophilus influenzae

ABSTRACT Clarithromycin-resistant Haemophilus influenzae strains with a nonsense mutation in acrR generally exhibited susceptibility to azithromycin, although one strain was found to be nonsusceptible; we aimed to clarify the differences. This strain had an amino acid substitution, Arg327Ser, in AcrB. Introduction of this substitution into H. influenzae Rd caused an increase in the MIC of azithromycin, suggesting that this substitution contributed to nonsusceptibility. These findings indicate that azithromycin-nonsusceptible isolates could occur through stepwise mutation in the acr region.

Short communication: Emergence of a new race of leaf rust with combined virulence to Lr14a and Lr72 genes on durum wheat

Leaf rust is a foliar disease caused by the fungus Puccinia triticina that may severely reduce durum wheat yield. Resistance to this pathogen is common in modern durum germplasm but is frequently based on Lr72 and Lr14a. After accounts of races with virulence to Lr14a gene in France in 2000, the present study reports the detection in 2013 for the first time of a new race with virulence to Lr14a and Lr72. The aim of this work was to characterize the virulence pattern of four Spanish isolates with virulence to Lr14a, and to discuss the consequences of this presence. Rusted leaves from cultivars ‘Don Jaime’ (Lr14a) and ‘Gallareta’ (Lr72) were collected in 2013 in the field at two Spanish sites, one in the south (near Cadiz) and another in the north (near Girona). Spores from single pustule for each cultivar and site were multiplied on susceptible cultivar ‘Don Rafael’. Then, the four isolates were inoculated on a set of 19 isogenic lines Thatcher to characterize their virulence spectrum. All isolates presented the same virulence pattern. They were virulent on both Lr14a and Lr72 and the race was named DBB/BS. This race was very similar to those reported in 2009-11, but with added virulence to Lr14a. The resistance based on Lr14a has therefore been overcome in Spain, by a new race that has likely emerged via stepwise mutation from the local predominating races. This information is important to guide breeders in their breeding programmes and gene deployment strategies.