Oligocene CO2 decline promoted C4 photosynthesis in grasses.

C4 photosynthesis is an adaptation derived from the more common C3 photosynthetic pathway that confers a higher productivity under warm temperature and low atmospheric CO2 concentration [1, 2]. C4 evolution has been seen as a consequence of past atmospheric CO2 decline, such as the abrupt CO2 fall 32-25 million years ago (Mya) [3-6]. This relationship has never been tested rigorously, mainly because of a lack of accurate estimates of divergence times for the different C4 lineages [3]. In this study, we inferred a large phylogenetic tree for the grass family and estimated, through Bayesian molecular dating, the ages of the 17 to 18 independent grass C4 lineages. The first transition from C3 to C4 photosynthesis occurred in the Chloridoideae subfamily, 32.0-25.0 Mya. The link between CO2 decrease and transition to C4 photosynthesis was tested by a novel maximum likelihood approach. We showed that the model incorporating the atmospheric CO2 levels was significantly better than the null model, supporting the importance of CO2 decline on C4 photosynthesis evolvability. This finding is relevant for understanding the origin of C4 photosynthesis in grasses, which is one of the most successful ecological and evolutionary innovations in plant history.

Cost evaluation and comparison of three decision strategies for cardiac revascularization : results of the suspected CAD protocol of the European CMR registry

Background: The public health burden of coronary artery disease (CAD) is important. Perfusion cardiac magnetic resonance (CMR) is generally accepted to detect and monitor CAD. Few studies have so far addressed its costs and costeffectiveness. Objectives: To compare in a large CMR registry the costs of a CMR-guided strategy vs two hypothetical invasive strategies for the diagnosis and the treatment of patients with suspected CAD. Methods: In 3'647 patients with suspected CAD included prospectively in the EuroCMR Registry (59 centers; 18 countries) costs were calculated for diagnostic examinations, revascularizations as well as for complication management over a 1-year follow-up. Patients with ischemia-positive CMR underwent an invasive X-ray coronary angiography (CXA) and revascularization at the discretion of the treating physician (=CMR+CXA strategy). Ischemia was found in 20.9% of patients and 17.4% of them were revascularized. In ischemia-negative patients by CMR, cardiac death and non-fatal myocardial infarctions occurred in 0.38%/y. In a hypothetical invasive arm the costs were calculated for an initial CXA followed by FFR testing in vessels with ≥50% diameter stenoses (=CXA+FFR strategy). To model this hypothetical arm, the same proportion of ischemic patients and outcome was assumed as for the CMR+CXA strategy. The coronary stenosis - FFR relationship reported in the literature was used to derive the proportion of patients with ≥50% diameter stenoses (Psten) in the study cohort. The costs of a CXA-only strategy were also calculated. Calculations were performed from a third payer perspective for the German, UK, Swiss, and US healthcare systems.