Biology subjects

Lucas, S. J.

Publications and source records attributed to Lucas, S. J..

3 recordsLinked to original sources

bioRxiv2019

A chromosome-scale genome assembly of European Hazel (Corylus avellana L.) reveals targets for crop improvement

European hazelnut (Corylus avellana L.) is a tree crop of economic importance worldwide, but especially to northern Turkey, where the majority of production takes place. Hazelnut production is currently challenged by environmental stresses such as a recent outbreak of severe powdery mildew disease; furthermore, allergy to hazelnuts is an increasing health concern in some regions.\n\nIn order to provide a foundation for utilizing the available hazelnut genetic resources for crop improvement, we produced the first fully assembled genome sequence and annotation for a hazelnut species, from Corylus avellana cv. Tombul, one of the most important Turkish varieties. A hybrid sequencing strategy combining short reads, long reads and proximity ligation methods enabled us to resolve heterozygous regions and produce a high-quality 370 Mb assembly that agrees closely with cytogenetic studies and genetic maps of the 11 C. avellana chromosomes, and covers 97.8% of the estimated genome size. The genome includes 28,409 high-confidence protein-coding genes, over 20,000 of which were functionally annotated based on homology to known plant proteins. We focused particularly on gene families encoding hazelnut allergens, and the MLO proteins that are an important susceptibility factor for powdery mildew. The complete assembly enabled us to differentiate between members of these families and identify novel homologs that may be important in mildew disease and hazelnut allergy. These findings provide examples of how the genome can be used to guide research and develop effective strategies for crop improvement in C. avellana.

genomics↗

bioRxiv2019

Genetic diversity and domestication of hazelnut (Corylus avellana) in Turkey

O_LIAssessing and describing genetic diversity in crop plants is a crucial first step towards their improvement. The European hazelnut, Corylus avellana, is one of the most economically important tree nut crops worldwide. It is primarily produced in Turkey where rural communities depend on it for their livelihoods. Despite this we know little about hazelnuts domestication history and the genetic diversity it holds.\nC_LIO_LIWe use double digest Restriction-site Associated DNA (ddRAD) sequencing to produce genome-wide dataset containing wild and domesticated hazelnut. We uncover patterns of population structure and diversity, determine levels of crop-wild gene flow and estimate the timing of key divergence events.\nC_LIO_LIWe find that genetic clusters of cultivars do not reflect their given names and that there is limited evidence for a reduction in genetic diversity in domesticated individuals. Admixture has likely occurred multiple times between wild and domesticated hazelnut. Domesticates appear to have first diverged from their wild relatives during the Mesolithic.\nC_LIO_LIWe provide the first genomic assessment of Turkish hazelnut diversity and suggest that it is currently in a partial stage of domestication. Our study provides a platform for further research that will protect this crop from the threats of climate change and an emerging fungal disease.\nC_LI

evolutionary biology↗

bioRxiv2017

Diminished dynamic cerebral autoregulatory capacity with forced oscillations in mean arterial pressure with elevated cardiorespiratory fitness

The effect that cardiorespiratory fitness has on the dynamic cerebral autoregulatory capacity during changes in mean arterial pressure (MAP) remains equivocal. Using a multiple-metrics approach, challenging MAP across the spectrum of physiological extremes (i.e. spontaneous through forced MAP oscillations), we characterized dynamic cerebral autoregulatory capacity in 19 male endurance athletes and 8 controls via three methods: [1] onset of regulation (i.e., time delay before an increase in middle cerebral artery (MCA) conductance [MCA flow velocity (MCAv)/mean arterial pressure (MAP)] and rate of regulation, after transient hypotension induced by sit-to-stand, and transfer function analysis (TFA) of MAP and MCAv responses during [2] spontaneous and [3] forced oscillations (5-min of squat-stand maneuvers performed at 0.05 and 0.10 Hz). Reductions in MAP and mean MCAv (MCAVmean) during initial orthostatic stress (0-30 s after sit-to-stand) and the prevalence of orthostatic hypotension were also determined. Onset of regulation was delayed after sit-to-stand in athletes (3.1{+/-}1.7 vs. 1.5{+/-}1.0 s; p=0.03), but rate of regulation was not different between groups (0.24{+/-}0.05 vs. 0.21{+/-}0.09 s-1; p=0.82). While both groups had comparable TFA metrics during spontaneous oscillations, athletes had higher TFA gain during 0.10 Hz squat-stand vs. recreational controls (p=0.01). Reductions in MAP (p=0.15) and MCAVmean (p=0.11) during orthostatic stress and the prevalence of initial orthostatic hypotension (p=0.65) were comparable between groups. These results indicate an intact ability of the cerebral vasculature to react to spontaneous oscillations but an attenuated capability to counter rapid and large changes in MAP in individuals with elevated cardiorespiratory fitness.\n\nNew findingsO_ST_ABSWhat is the central question of this study?C_ST_ABSO_LIWhat is the impact of cardiorespiratory fitness on dynamic cerebral autoregulatory capacity?\nC_LI\n\nWhat is the main finding and its importance?O_LIOur results indicate an intact ability of the cerebral vasculature to react to spontaneous oscillations but an attenuated capability to counter rapid and large changes in mean arterial pressure in individuals with elevated cardiorespiratory fitness.\nC_LI

physiology↗