Societal Impact Statement: The current ash dieback epidemic in Europe caused by Hymenoscyphus fraxineus poses a key question to policy makers: whether or not to commit time and resources to the initiation of a breeding programme for the development of more resistant ash, as a long‐term policy of adaptation to the epidemic. Here we review current evidence on the potential viability of such a programme, from a biological perspective. We conclude that a breeding programme for ash aimed at resistance to current strains of H. fraxineus in the British Isles is biologically feasible.Summary: To evaluate the viability and feasibility of a future breeding programme to produce trees resistant to an emerging pest or pathogen, it is helpful to ask the following questions: How much variation in resistance exists in tree populations? To what extent is this resistance heritable? How many genetic loci are involved? What level of resistance is found in other species of the same genus? Here, we survey current knowledge of these issues in relation to the degree of resistance of European ash (Fraxinus excelsior) to H. fraxineus, the fungus causing ash dieback (ADB). Several studies have found a low frequency of heritable resistance in F. excelsior populations, which seems to be determined by many genetic loci. This suggests that a breeding programme is viable and that natural selection may also increase the mean resistance of populations over time. More research is needed on the genetic basis of resistance to ADB to understand how quickly natural selection can operate in woodlands and what acceleration may be possible in breeding programmes, including via use of genetic markers. Hybrid breeding programmes may also be a possibility, as some ash species appear to be more resistant to ADB than is F. excelsior, but more research is needed on this issue. We do not yet know if it will be possible to breed F. excelsior to have resistance to both ADB and the emerging threat of emerald ash borer. We recommend short‐term mitigation measures for the ADB epidemic and future research directions.

Background: Obesity and type 2 diabetes (T2DM) are increasing in Saudi Arabia (SA). Among other conditions, these risk factors increase the likelihood of non-alcoholic fatty liver disease (NAFLD), which in turn increases risks for advanced liver diseases, such as non-alcoholic steatohepatitis (NASH), cirrhosis and cancer. The goal of this study was to quantify the health and economic burden of obesity-attributable T2DM and liver disease in SA.Methods: We developed a microsimulation of the SA population to quantify the future incidence and direct health care costs of obesity-attributable T2DM and liver disease, including liver cancer. Model inputs included population demographics, body mass index, incidence, mortality and direct health care costs of T2DM and liver disease and relative risks of each condition as a function of BMI category. Model outputs included age- and sex-disaggregated incidence of obesity-attributable T2DM and liver disease and their direct health care costs for SA’s working-age population (20–59 years) between 2020 and 2040.Results: Between 2020 and 2040, the available data predicts 1,976,593 [± 1834] new cases of T2DM, 285,346 [±874] new cases of chronic liver diseases, and 2,101 [± 150] new cases of liver cancer attributable to obesity, amongst working-age people. By 2040, the direct health care costs of these obesity-attributable diseases are predicted to be 127,956,508,540 [± 51,882,446] USD.Conclusions: The increase in obesity-associated T2DM and liver disease emphasises the urgent need for obesity interventions and strategies to meaningfully reduce the future health and economic burden of T2DM, chronic liver diseases and liver cancer in SA.

Acute Oak Decline (AOD) is complex syndrome affecting Britain’s keystone native oak species, (Quercus robur L. and Q. petraea L. (Matt.) Liebl.), in some cases causing mortality within five years of symptom development. The most distinguishable symptom is weeping stem lesions, from which four species of bacteria have been isolated: Brenneria goodwinii, Gibbsiella quercinecans, Lonsdalea britannica and Rahnella victoriana. We do not yet know where else these bacteria exist, and little is known about the relationship of the wider oak leaf microbiome (phyllosphere) to acute oak decline. Here we investigate whether incidental evidence from a large oak genome re-sequencing dataset could be used to detect these bacteria in oak foliage, and whether bacterial incidence co-varied with AOD status or location. Oak leaves and buds were sampled from 421 trees at five sites in England. Whole genomic DNA from these samples was shot-gun sequenced with short reads. Non-oak reads were extracted from these data and queried to microbial databases. Reads uniquely matching AOD-associated bacterial genomes were found to be present on trees from all five sites and included trees with active lesions, trees with historic lesions and trees without AOD symptoms. The abundance of the AOD-associated bacteria did not differ between tree health categories but did differ among sites. We conclude that the AOD-associated bacteria may be members of the normal oak microbiome, whose presence on a tree is not sufficient to cause AOD symptoms.

Changes in gene expression form a crucial part of the plant response to infection. In the last decade, whole-leaf expression profiling has played a valuable role in identifying genes and processes that contribute to the interactions between the model plant Arabidopsis thaliana and a diverse range of pathogens. However, with some pathogens such as downy mildew caused by the biotrophic oomycete pathogen Hyaloperonospora arabidopsidis (Hpa), whole-leaf profiling may fail to capture the complete Arabidopsis response encompassing responses of non-infected as well as infected cells within the leaf. Highly localized expression changes that occur in infected cells may be diluted by the comparative abundance of non-infected cells. Furthermore, local and systemic Hpa responses of a differing nature may become conflated. To address this we applied the technique of Fluorescence Activated Cell Sorting (FACS), typically used for analyzing plant abiotic responses, to the study of plant-pathogen interactions. We isolated haustoriated (Hpa-proximal) and non-haustoriated (Hpa-distal) cells from infected seedling samples using FACS, and measured global gene expression. When compared with an uninfected control, 278 transcripts were identified as significantly differentially expressed, the vast majority of which were differentially expressed specifically in Hpa-proximal cells. By comparing our data to previous, whole organ studies, we discovered many highly locally regulated genes that can be implicated as novel in the Hpa response, and that were uncovered for the first time using our sensitive FACS technique.

Societal Impact Statement: The largest populations of veteran oak trees in Europe are found in British parklands: managed wood pastures up to 1000 years old. Here, we present genomic evidence that parkland oak populations harbour considerable diversity and grew from local seed sources. We found some evidence for natural regeneration of offspring and for hybridization between pedunculate and sessile oak. We detected signatures of past gene flow between these two species and few regions of high differentiation within their genomes. Future expansion of this dataset may allow us to test for a genomic basis of acute oak decline, a syndrome of particular concern in parkland environments.Summary: The two predominant oak species in Europe, Quercus robur (English or pedunculate oak) and Quercus petraea (sessile oak), have a long history of human intervention. In Britain, a common management regime is parklands, often surrounding country houses. Little is known about how seeds were sourced for parkland oak populations nor the genetic diversity that they contain. We sequenced the whole genomes of 386 trees from four British parkland sites to characterize the nuclear and chloroplast genetic structure and diversity of oak parkland populations. We assembled the chloroplast genomes and matched these to restriction enzyme fragment chloroplast haplotypes found in previous studies of ancient woodlands. We found over two million high‐quality nuclear single‐nucleotide polymorphisms (SNPs), allowing us to identify 360 Q. robur, 10 Q. petraea and 16 hybrid individuals with confidence. We identified 81 coding regions exhibiting strong differentiation between the two species. We found evidence for selective sweeps in Q. robur near some regions containing genes with putative involvement in stress tolerance. We detected a few very close relatives within some sites, suggesting natural regeneration or local seed planting. There was little differentiation among the Q. robur populations at the four sites. Chloroplast genomes found in each parkland tended to be similar to those of local ancient woodlands, suggesting that they were derived from local seed sources.

Damage is an inevitable consequence of life. For unicellular organisms, this leads to a trade-off between allocating resources into damage repair or into growth coupled with segregation of damage upon cell division, i.e., aging and senescence. Few studies considered repair as an alternative to senescence. None considered biofilms, where the majority of unicellular organisms live, although fitness advantages in well-mixed systems often turn into disadvantages in spatially structured systems such as biofilms. We compared the fitness consequences of aging versus an adaptive repair mechanism based on sensing damage, using an individual-based model of a generic unicellular organism growing in biofilms. We found that senescence is not beneficial provided that growth is limited by substrate availability. Instead, it is useful as a stress response to deal with damage that failed to be repaired when (i) extrinsic mortality was high; (ii) a degree of multicellularity was present; and (iii) damage segregation was effective.