Testing the possibility for photosynthetic compensation in an alga-invertebrate symbiosis under thermal stress: implications for carbon production and translocation

Warner, Mark E.Thermal stress is driving the global decline in reef coral growth and survival. These cnidarians possess different levels of thermal tolerance driven, in part, by the symbiotic dinoflagellates they host. Chlorophyll a fluorescence is often used to assess photo-stress in these symbiotic algae. However, the underlying implications of photo-stress and how it affects downstream carbon production and translocation to the host have yet to be investigated. Active PSII reaction centers were manipulated in a thermally tolerant and thermally sensitive strain of Breviolum minutum by chemical inhibition with DCMU to examine how chlorophyll fluorescence, photosynthetic efficiency (α), and maximal photosynthesis (Pmax) changed. These parameters were then used to examine possible compensatory electron flow in steady-state electron turnover through functional PSII reaction centers (1/τPSII). In addition, acute heating response in vitro, as well as chronic heating of intact symbioses, were used to compare the effects of thermal stress and the relationship between PSII reaction center inactivation and other measures of photosynthesis. Values for α and Pmax declined with increasing DCMU more rapidly in the thermally susceptible symbiont strain than in the thermally tolerant strain with similar results seen both in vitro and in hospite. The thermally tolerant symbiont maintained carbon translocation during experimental heating, while translocation decreased in the thermally susceptible symbiont. Manipulation of PSII photochemistry by chemical titration or experimental heating provided evidence that the thermally tolerant symbiont sustained photochemical efficiency better than the thermally susceptible alga by maintaining or increasing compensatory electron flow.University of Delaware, School of Marine Science and PolicyM.S

Polygenic risk scores for prediction of breast cancer and breast cancer subtypes

Abstract Stratification of women according to their risk of breast cancer based on polygenic risk scores (PRSs) could improve screening and prevention strategies. Our aim was to develop PRSs, optimized for prediction of estrogen receptor (ER)-specific disease, from the largest available genome-wide association dataset and to empirically validate the PRSs in prospective studies. The development dataset comprised 94,075 case subjects and 75,017 control subjects of European ancestry from 69 studies, divided into training and validation sets. Samples were genotyped using genome-wide arrays, and single-nucleotide polymorphisms (SNPs) were selected by stepwise regression or lasso penalized regression. The best performing PRSs were validated in an independent test set comprising 11,428 case subjects and 18,323 control subjects from 10 prospective studies and 190,040 women from UK Biobank (3,215 incident breast cancers). For the best PRSs (313 SNPs), the odds ratio for overall disease per 1 standard deviation in ten prospective studies was 1.61 (95%CI: 1.57–1.65) with area under receiver-operator curve (AUC) = 0.630 (95%CI: 0.628–0.651). The lifetime risk of overall breast cancer in the top centile of the PRSs was 32.6%. Compared with women in the middle quintile, those in the highest 1% of risk had 4.37- and 2.78-fold risks, and those in the lowest 1% of risk had 0.16- and 0.27-fold risks, of developing ER-positive and ER-negative disease, respectively. Goodness-of-fit tests indicated that this PRS was well calibrated and predicts disease risk accurately in the tails of the distribution. This PRS is a powerful and reliable predictor of breast cancer risk that may improve breast cancer prevention programs