Massively parallel sequencing and analysis of expressed sequence tags in a successful invasive plant

Background Invasive species pose a significant threat to global economies, agriculture and biodiversity. Despite progress towards understanding the ecological factors associated with plant invasions, limited genomic resources have made it difficult to elucidate the evolutionary and genetic factors responsible for invasiveness. This study presents the first expressed sequence tag (EST) collection for Senecio madagascariensis, a globally invasive plant species. Methods We used pyrosequencing of one normalized and two subtractive libraries, derived from one native and one invasive population, to generate an EST collection. ESTs were assembled into contigs, annotated by BLAST comparison with the NCBI non-redundant protein database and assigned gene ontology (GO) terms from the Plant GO Slim ontologies. Key Results Assembly of the 221 746 sequence reads resulted in 12 442 contigs. Over 50 % (6183) of 12 442 contigs showed significant homology to proteins in the NCBI database, representing approx. 4800 independent transcripts. The molecular transducer GO term was significantly over-represented in the native (South African) subtractive library compared with the invasive (Australian) library. Based on NCBI BLAST hits and literature searches, 40 % of the molecular transducer genes identified in the South African subtractive library are likely to be involved in response to biotic stimuli, such as fungal, bacterial and viral pathogens. Conclusions This EST collection is the first representation of the S. madagascariensis transcriptome and provides an important resource for the discovery of candidate genes associated with plant invasiveness. The over-representation of molecular transducer genes associated with defence responses in the native subtractive library provides preliminary support for aspects of the enemy release and evolution of increased competitive ability hypotheses in this successful invasive. This study highlights the contribution of next-generation sequencing to better understanding the molecular mechanisms underlying ecological hypotheses that are important in successful plant invasions

Impacts of human-induced environmental disturbances on hybridization between two ecologically differentiated Californian oak species

Natural hybridization, which can be involved in local adaptation and in speciation processes, has been linked to different sources of anthropogenic disturbance. Here, we use genotypic data to study range-wide patterns of genetic admixture between the serpentine-soil specialist leather oak (Quercus durata) and the widespread Californian scrub oak (Quercus berberidifolia). First, we estimated hybridization rates and the direction of gene flow. Second, we tested the hypothesis that genetic admixture increases with different sources of environmental disturbance, namely anthropogenic destruction of natural habitats and wildfire frequency estimated from long-term records of fire occurrence. Our analyses indicate considerable rates of hybridization (> 25%), asymmetric gene flow from Q. durata into Q. berberidifolia, and a higher occurrence of hybrids in areas where both species live in close parapatry. In accordance with the environmental disturbance hypothesis, we found that genetic admixture increases with wildfire frequency, but we did not find a significant effect of other sources of human-induced habitat alteration (urbanization, land clearing for agriculture) or a suite of ecological factors (climate, elevation, soil type). Our findings highlight that wildfires constitute an important source of environmental disturbance, promoting hybridization between two ecologically well-differentiated native species.Peer reviewe

First dose of potential new medicines to humans: How animals help

The need for careful testing of new drugs in animal models before study in humans has been recognised by physicians since the First World War. Now, first human studies on new drugs are subject to detailed government guidelines, which in the European Union are presently being reinforced through the wide-ranging Clinical Trials Directive. However, despite their long history and widespread application, these guidelines are empirical and have been formulated with a paucity of critical scientific evidence. Here, we review the principles and the available, albeit limited, evidence that support the design and conduct of preclinical studies in a way that permits effective and safe first-dose studies of potential new medicines in humans

Genetic analysis of the dry forest timber tree Sideroxylon capiri in Costa Rica using AFLP

Sideroxylon capiri (“Tempisque”) is a threatened and economically important timber species in the dry forest of Costa Rica. To assess the extent of the genetic diversity between and within populations of this species, 86 samples were obtained from four sites in the northwestern part of the country from protected and non-protected areas. They were analyzed by amplified fragment length polymorphism. Five primers were used to generate 254 polymorphic bands. Molecular variance indicated a 92 % within locations with a PhiPT (φ st) of 0.083 and a He from 0.204 to 0.249. PCoA analysis showed two different groups: one formed by Palo Verde and La Cruz samples, and another group with Nicoya and Barra Honda samples. The dendrogram arranged the samples in three groups: individuals from Palo Verde and La Cruz divided in two groups, and a more compact group from Barra Honda and Nicoya. A positive correlation between pairwise linearized geographical distance and genetic differentiation among populations was detected by Mantel test (R 2 = 0.76241, P = 0.04). Results are discussed in terms of fragmentation of the continuous forests and geographical barriers. Despite these results, it is evident that a great genetic diversity exists for this species and the results can be used for conservation purposes.Universidad de Costa Rica/[]/UCR/Costa RicaConsejo Nacional para Investigaciones Científicas y Tecnológicas/[]/CONICIT/Costa RicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Biología Celular y Molecular (CIBCM)UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de QuímicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí