Morphometric and molecular variation in concert: taxonomy and genetics of the reticulate Pyrenean and Iberian alpine spiny fescues (Festuca eskia complex,Poaceae)

The Iberian mountain spiny fescues are a reticulate group of five diploid grass taxa consisting of three parental species and two putative hybrids: F. × souliei (F. eskia × F. quadriflora) and F. × picoeuropeana (F. eskia × F. gautieri). Phenotypic and molecular studies were conducted with the aim of determining the taxonomic boundaries and genetic relationships of the five taxa and disentangling the origins of the two hybrids. Statistical analyses of 31 selected phenotypic traits were conducted on individuals from 159 populations and on nine type specimens. Molecular analyses of random amplified polymorphic DNA (RAPD) markers were performed on 29 populations. The phenotypic analyses detected significant differences between the five taxa and demonstrated the overall intermediacy of the F. × picoeuropeana and F. × souliei between their respective parents. The RAPD analysis corroborated the genetic differentiation of F. eskia, F. gautieri and F. quadriflora and the intermediate nature of the two hybrids; however, they also detected genetic variation within F. × picoeuropeana. These results suggest distinct origins for F. × picoeuropeana in the Cantabrian and Pyrenean mountains, with the sporadic Pyrenean populations having potentially resulted from recent hybridizations and the stabilized Cantabrian ones from older events followed by potential displacements of the parents. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173 , 676–706.     

First report of Bombus terrestris xanthopus Kriechbaumer on the Italian peninsula (Hymenoptera: Apidae)

A male specimen of Bombus terrestris (L. 1758) showing an intermediate colour between the subspecies xanthopus Kriechbaumer 1870 endemic to Corsica and the subspecies terrestris ubiquitous in the mainland was found within samples collected in 1999 on the Tuscan coast. Hybrid specimens between these subspecies are common on some of the islands of the Tuscan archipelago, while others only have pure populations. The finding is significant as it could signal the spread of the subspecies xanthopus_to the mainland. We consider and discuss the circumstances of the finding.     

Phylogeographical pattern of Euplotes nobilii,a protist ciliate with a bipolar biogeographical distribution

Nuclear (18S and ITS) and mitochondrial (16S) ribosomal RNA gene sequences were determined from genetically distinct wild‐type strains of Antarctic (nine strains), Fuegian (four strains), Greenland (nine strains) and Svalbard (three strains) populations of the marine ciliate, Euplotes nobilii, and analysed for their nucleotide polymorphisms. A close genetic homogeneity was found within and between the Antarctic and Fuegian populations, while more significant levels of genetic differentiation were detected within and between the two Arctic populations, as well as between these populations and the Antarctic/Fuegian ones. The phylogeographical pattern that was derived from these data indicates that gene flow is not limited among Arctic populations; it equally connects the Arctic and Antarctic populations either directly, or through the Fuegian population. This indication reinforces previous evidence from laboratory assays of mating interactions between some of the strains analysed in this work that Southern and Northern polar populations of E. nobilii belong to a unique, panmictic population that substantially share the same gene pool.     

Inheritance patterns of ITS1, chloroplasts and mitochondria in artificial hybrids of the seaweeds Fucus serratus and F. evanescens (Phaeophyceae)

Patterns of nuclear and organelle inheritance among artificial hybrids of the seaweeds Fucus serratus and F. evanescens were detected using single-strand conformation polymorphism (SSCP). Three alleles were identified in the 231?bp rDNA-ITS1 gene (nuclear): two in F. serratus and one in F. evanescens. Alleles differed by 1–2?bp and all hybrids possessed one allele from each parent. Two haplotypes were present in the 288?bp Rubisco spacer (chloroplast), differentiated by a 33?bp indel. Two haplotypes differing by a single nucleotide were found in a 135?bp region of nad11 gene (mitochondrion). Both organelles are maternally inherited, as all hybrids contained the haplotypes of the parent contributing the egg. Although laboratory hybrids among Fucus spp. have been produced previously, this is the first time that both nuclear and cytoplasmic genetic markers have been used to document inheritance patterns. SSCPs analysed on an automated sequencer offer a rapid and powerful approach for identifying suspected hybrids from field samples, as well as a screen for intraspecific and intra-individual variation in DNA regions prior to confirmation of variations by sequencing.     

The sub‐nanomolar binding of DNA–RNA hybrids by the single‐chain Fv fragment of antibody S9.6

The monoclonal antibody S9.6 binds DNA–RNA hybrids with high affinity, making it useful in research and diagnostic applications, such as in microarrays and in the detection of R‐loops. A single‐chain variable fragment (scFv) of S9.6 was produced, and its affinities for various synthetic nucleic acid hybrids were measured by surface plasmon resonance (SPR). S9.6 exhibits dissociation constants of approximately 0.6 nM for DNA–RNA and, surprisingly, 2.7 nM for RNA–RNA hybrids that are AU‐rich. The affinity of the S9.6 scFv did not appear to be strongly influenced by various buffer conditions or by ionic strength below 500 mM NaCl. The smallest epitope that was strongly bound by the S9.6 scFv contained six base pairs of DNA–RNA hybrid. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.     

A genetically distinct hybrid zone occurs for two globally invasive mosquito fish species with striking phenotypic resemblance

Hybrid zones allow for the investigation of incipient speciation and related evolutionary processes of selection, gene flow, and migration. Interspecific dynamics, like competition, can impact the size, shape, and directional movement of species in hybrid zones. Hybrid zones contribute to a paradox for the biological species concept because interbreeding between species occurs while parental forms remain distinct. A long‐standing zone of intergradation or introgression exists for eastern and western mosquito fish (Gambusia holbrooki and G. affinis) around Mobile Bay, AL. The region has been studied episodically, over decades, making it perfect for addressing temporal dynamics and for providing a deeper understanding of the genetics of these periodically reclassified fishes (as species or subspecies). We used six microsatellite markers to assess the current population structure and gene flow patterns across 19 populations of mosquito fish and then compared our results with historical data. Genetic evidence demonstrates that the current hybrid zone is located in a similar geographic region as the historical one, even after three decades. Hybrid fish, however, demonstrate relatively low heterozygosity and are genetically distinct from western and eastern mosquito fish populations. Fin ray counts, sometimes used to distinguish the two species from one another, demonstrate more eastern (G. holbrooki) phenotype fish within the molecular genetic hybrid zone today. Mosquito fish are globally invasive, often found on the leading edge of flooded waters that they colonize, so the impact of hurricanes in the wake of climate change was also evaluated. An increase in the frequency and intensity of hurricanes in the hybrid region has occurred, and this point warrants further attention since hurricanes are known to move these aggressive, invasive species into novel territory. This work contributes to our classical understanding of hybrid zone temporal dynamics, refines our understanding of mosquito fish genetics in their native range, evaluates important genotype–phenotype relationships, and identifies a potential new impact of climate change.     

The TaDREB3 transgene transferred by conventional crossings to different genetic backgrounds of bread wheat improves drought tolerance

Drought tolerance of the wheat cultivar Bobwhite was previously enhanced by transformation with a construct containing the wheat DREB3 gene driven by the stress‐inducible maize Rab17 promoter. Progeny of a single T₂ transgenic line were used as pollinators in crosses with four elite bread wheat cultivars from Western Australia: Bonnie Rock, IGW‐2971, Magenta and Wyalkatchem, with the aim of evaluating transgene performance in different genetic backgrounds. The selected pollinator line, BW8‐9‐10‐3, contained multiple transgene copies, had significantly improved drought tolerance compared with wild‐type plants and showed no growth and development penalties or abnormalities. A single hybrid plant was selected from each cross‐combination for three rounds of backcrossing with the corresponding maternal wheat cultivar. The transgene was detected in all four F₁BC₃ combinations, but stress‐inducible transgene expression was found in only three of the four combinations. Under well‐watered conditions, the phenotypes and grain yield components of the F₂BC₃ transgene‐expressing lines were similar to those of corresponding recurrent parents and null‐segregants. Under severe drought conditions, the backcross lines demonstrated 12–18% higher survival rates than the corresponding control plants. Two from four F₃BC₃ transgenic lines showed significantly higher yield (18.9% and 21.5%) than control plants under limited water conditions. There was no induction of transgene expression under cold stress, and therefore, no improvement of frost tolerance observed in the progenies of drought‐tolerant F₃BC₃ lines.     

A metabolome‐based core hybridisation strategy for the prediction of rice grain weight across environments

Marker‐based prediction holds great promise for improving current plant and animal breeding efficiencies. However, the predictabilities of complex traits are always severely affected by negative factors, including distant relatedness, environmental discrepancies, unknown population structures, and indeterminate numbers of predictive variables. In this study, we utilised two independent F₁ hybrid populations in the years 2012 and 2015 to predict rice thousand grain weight (TGW) using parental untargeted metabolite profiles with a partial least squares regression method. A stable predictive model for TGW was built based on hybrids from the population in 2012 (r = 0.75) but failed to properly predict TGW for hybrids from the population in 2015 (r = 0.27). After integrating hybrids from both populations into the training set, the TGW of hybrids could be predicted but was largely dependent on population structures. Then, core hybrids from each population were determined by principal component analysis and the TGW of hybrids in both environments were successfully predicted (r > 0.60). Moreover, adjusting the population structures and numbers of predictive analytes increased TGW predictability for hybrids in 2015 (r = 0.72). Our study demonstrates that the TGW of F₁ hybrids across environments can be accurately predicted based on parental untargeted metabolite profiles with a core hybridisation strategy in rice. Metabolic biomarkers identified from early developmental stage tissues, which are grown under experimental conditions, may represent a workable approach towards the robust prediction of major agronomic traits for climate‐adaptive varieties.     

Efficient Pre-mRNA Cleavage Prevents Replication-Stress-Associated Genome Instability

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