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292 result(s) for "Cooper, Martha"
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Lagging adaptation to warming climate in Arabidopsis thaliana
If climate change outpaces the rate of adaptive evolution within a site, populations previously well adapted to local conditions may decline or disappear, and banked seeds from those populations will be unsuitable for restoring them. However, if such adaptational lag has occurred, immigrants from historically warmer climates will outperform natives and may provide genetic potential for evolutionary rescue. We tested for lagging adaptation to warming climate using banked seeds of the annual weed Arabidopsis thaliana in common garden experiments in four sites across the species’ native European range: Valencia, Spain; Norwich, United Kingdom; Halle, Germany; and Oulu, Finland. Genotypes originating from geographic regions near the planting site had high relative fitness in each site, direct evidence for broad-scale geographic adaptation in this model species. However, genotypes originating in sites historically warmer than the planting site had higher average relative fitness than local genotypes in every site, especially at the northern range limit in Finland. This result suggests that local adaptive optima have shifted rapidly with recent warming across the species’ native range. Climatic optima also differed among seasonal germination cohorts within the Norwich site, suggesting that populations occurring where summer germination is common may have greater evolutionary potential to persist under future warming. If adaptational lag has occurred over just a few decades in banked seeds of an annual species, it may be an important consideration for managing longer-lived species, as well as for attempts to conserve threatened populations through ex situ preservation.
Supply Chain Management: It's All About the Journey, Not the Destination
With over three decades of the use of the term “supply chain management,” five academic and practitioner perspectives of supply chain management are described. Much ink has been devoted to defining and developing the concept and analyzing its use or nonuse. The focus of this article is on academic effort, with suggestions of how to proceed in the future.
Large-effect flowering time mutations reveal conditionally adaptive paths through fitness landscapes in Arabidopsis thaliana
Contrary to previous assumptions that most mutations are deleterious, there is increasing evidence for persistence of large-effect mutations in natural populations. A possible explanation for these observations is that mutant phenotypes and fitness may depend upon the specific environmental conditions to which a mutant is exposed. Here, we tested this hypothesis by growing large-effect flowering time mutants of Arabidopsis thaliana in multiple field sites and seasons to quantify their fitness effects in realistic natural conditions. By constructing environment-specific fitness landscapes based on flowering time and branching architecture, we observed that a subset of mutations increased fitness, but only in specific environments. These mutations increased fitness via different paths: through shifting flowering time, branching, or both. Branching was under stronger selection, but flowering time was more genetically variable, pointing to the importance of indirect selection on mutations through their pleiotropic effects on multiple phenotypes. Finally, mutations in hub genes with greater connectedness in their regulatory networks had greater effects on both phenotypes and fitness. Together, these findings indicate that large-effect mutations may persist in populations because they influence traits that are adaptive only under specific environmental conditions. Understanding their evolutionary dynamics therefore requires measuring their effects in multiple natural environments.
Novel antiinflammatory biologics shaped by parasite—host coevolution
Parasitic helminth infections, while a major cause of neglected tropical disease burden, negatively correlate with the incidence of immune-mediated inflammatory diseases such as inflammatory bowel diseases (IBD). To evade expulsion, helminths have developed sophisticated mechanisms to regulate their host’s immune responses. Controlled experimental human helminth infections have been assessed clinically for treating inflammatory conditions; however, such a radical therapeutic modality has challenges. An alternative approach is to harness the immunomodulatory properties within the worm’s excretory—secretory (ES) complement, its secretome. Here, we report a biologics discovery and validation pipeline to generate and screen in vivo a recombinant cell-free secretome library of helminth-derived immunomodulatory proteins. We successfully expressed 78 recombinant ES proteins from gastrointestinal hookworms and screened the crude in vitro translation reactions for anti-IBD properties in a mouse model of acute colitis. After statistical filtering and ranking, 20 proteins conferred significant protection against various parameters of colitis. Lead candidates from distinct protein families, including annexins, transthyretins, nematode-specific retinol-binding proteins, and SCP/TAPS were identified. Representative proteins were produced in mammalian cells and further validated, including ex vivo suppression of inflammatory cytokine secretion by T cells from IBD patient colon biopsies. Proteins identified herein offer promise as novel, safe, and mechanistically differentiated biologics for treating the globally increasing burden of inflammatory diseases.
Effects of Genetic Perturbation on Seasonal Life History Plasticity
Like many species, the model plant Arabidopsis thaliana exhibits multiple different life histories in natural environments. We grew mutants impaired in different signaling pathways in field experiments across the species' native European range in order to dissect the mechanisms underlying this variation. Unexpectedly, mutational loss at loci implicated in the cold requirement for flowering had little effect on life history except in late-summer cohorts. A genetically informed photothermal model of progression toward flowering explained most of the observed variation and predicted an abrupt transition from autumn flowering to spring flowering in late-summer germinants. Environmental signals control the timing of this transition, creating a critical window of acute sensitivity to genetic and climatic change that may be common for seasonally regulated life history traits.
Phenological and fitness responses to climate warming depend upon genotype and competitive neighbourhood in Arabidopsis thaliana
Increasing temperatures during climate change are known to alter the phenology across diverse plant taxa, but the evolutionary outcomes of these shifts are poorly understood. Moreover, plant temperature‐sensing pathways are known to interact with competition‐sensing pathways, yet there remains little experimental evidence for how genotypes varying in temperature responsiveness react to warming in realistic competitive settings. We compared flowering time and fitness responses to warming and competition for two near‐isogenic lines (NILs) of Arabidopsis thaliana transgressively segregating temperature‐sensitive and temperature‐insensitive alleles for major‐effect flowering time genes. We grew focal plants of each genotype in intraspecific and interspecific competition in four treatments contrasting daily temperature profiles in summer and fall under contemporary and warmed conditions. We measured phenology and fitness of focal plants to quantify plastic responses to season, temperature and competition and the dependence of these responses on flowering time genotype. The temperature‐insensitive NIL was constitutively early flowering and less fit, except in a future‐summer climate in which its fitness was higher than the later flowering, temperature‐sensitive NIL in low competition. The late‐flowering NIL showed accelerated flowering in response to intragenotypic competition and to increased temperature in the summer but delayed flowering in the fall. However, its fitness fell with rising temperatures in both seasons, and in the fall its marginal fitness gain from decreasing competition was diminished in the future. Functional alleles at temperature‐responsive genes were necessary for plastic responses to season, warming and competition. However, the plastic genotype was not the most fit in every experimental condition, becoming less fit than the temperature‐canalized genotype in the warm summer treatment. Climate change is often predicted to have deleterious effects on plant populations, and our results show how increased temperatures can act through genotype‐dependent phenology to decrease fitness. Furthermore, plasticity is not necessarily adaptive in rapidly changing environments since a nonplastic genotype proved fitter than a plastic genotype in a warming climate treatment. A plain language summary is available for this article. Plain Language Summary
Mucosal delivery of ESX-1–expressing BCG strains provides superior immunity against tuberculosis in murine type 2 diabetes
Tuberculosis (TB) claims 1.5 million lives per year. This situation is largely due to the low efficacy of the only licensed TB vaccine, Bacillus Calmette–Guérin (BCG) against pulmonary TB. The metabolic disease type 2 diabetes (T2D) is a risk factor for TB and the mechanisms underlying increased TB susceptibility in T2D are not well understood. Furthermore, it is unknown if new TB vaccines will provide protection in the context of T2D. Herewe used a diet-induced murine model of T2D to investigate the underlying mechanisms of TB/T2D comorbidity and to evaluate the protective capacity of two experimental TB vaccines in comparison to conventional BCG. Our data reveal a distinct immune dysfunction that is associated with diminished recognition of mycobacterial antigens in T2D. More importantly, we provide compelling evidence that mucosal delivery of recombinant BCG strains expressing the Mycobacterium tuberculosis (Mtb) ESX-1 secretion system (BCG::RD1 and BCG::RD1 ESAT-6 Δ92–95) are safe and confer superior immunity against aerosol Mtb infection in the context of T2D. Our findings suggest that the remarkable anti-TB immunity by these recombinant BCG strains is achieved via augmenting the numbers and functional capacity of antigen presenting cells in the lungs of diabetic mice.
Interacting effects of genetic variation for seed dormancy and flowering time on phenology, life history, and fitness of experimental Arabidopsis thaliana populations over multiple generations in the field
Major alleles for seed dormancy and flowering time are well studied, and can interact to influence seasonal timing and fitness within generations. However, little is known about how this interaction controls phenology, life history, and population fitness across multiple generations in natural seasonal environments. To examine how seed dormancy and flowering time shape annual plant life cycles over multiple generations, we established naturally dispersing populations of recombinant inbred lines of Arabidopsis thaliana segregating early and late alleles for seed dormancy and flowering time in a field experiment. We recorded seasonal phenology and fitness of each genotype over 2 yr and several generations. Strong seed dormancy suppressed mid-summer germination in both early- and late-flowering genetic backgrounds. Strong dormancy and late-flowering genotypes were both necessary to confer a winter annual life history; other genotypes were rapid-cycling. Strong dormancy increased within-season fecundity in an early-flowering background, but decreased it in a late-flowering background. However, there were no detectable differences among genotypes in population growth rates. Seasonal phenology, life history, and cohort fitness over multiple generations depend strongly upon interacting genetic variation for dormancy and flowering. However, similar population growth rates across generations suggest that different life cycle genotypes can coexist in natural populations.