Convergence across biomes to a common rain-use efficiency

Water availability limits plant growth and production in almost all terrestrial ecosystems. However, biomes differ substantially in sensitivity of aboveground net primary production (ANPP) to between-year variation in precipitation. Average rain-use efficiency (RUE; ANPP/precipitation) also varies between biomes, supposedly because of differences in vegetation structure and/or biogeochemical constraints. Here we show that RUE decreases across biomes as mean annual precipitation increases. However, during the driest years at each site, there is convergence to a common maximum RUE (RUE(max)) that is typical of arid ecosystems. RUE(max) was also identified by experimentally altering the degree of limitation by water and other resources. Thus, in years when water is most limiting, deserts, grasslands and forests all exhibit the same rate of biomass production per unit rainfall, despite differences in physiognomy and site-level RUE. Global climate models predict increased between-year variability in precipitation, more frequent extreme drought events, and changes in temperature. Forecasts of future ecosystem behaviour should take into account this convergent feature of terrestrial biomes.     

Tolerance of red cell antigens and transplantation immunity in chickens

Résumé L'injection d'érythrocytes de la poule adulte à poussins récemment éclos abaisse sérieusement leur capacité de repondre dorénavant à l'immunisation active par la formation d'iso-agglutinines.La tolérance à l'égard d'homéogreffes de peau n'est en rien due aux érythrocytes, mais exclusivement aux leucocytes.Nous tirons de ces faits la conclusion que la formation d'isoagglutinines et la réaction conduisant à la destruction d'homéogreffes cutanées représentent deux modes de réponse immunologique nettement différents.     

Enriching Service-Learning by Developing e-Tutoring in Foster Homes

In view of the learning divide between the children in ordinary families and those in foster homes, online one-to-one tutoring has been provided by university students as a service-learning option. Through the synchronous e-tutoring system platform, the goal of this study is to develop a service learning mode for creating campus-community partnerships and mutual learning experiences. Thus the study applies Ramsden’s theory of university teaching (2003) into an action research project for investigating (i) how e-tutoring can solve the problems occurring in face-to-face tutoring in foster homes; (ii) the effects of e-tutoring; (iii) the new issues identified; and (iv) new strategies for future iterations of the program. For explaining a social phenomenon through a theoretical framework, grounded theory analysis was applied and eight themes were identified in the qualitative data of 10 observation reports, 28 interviews, and 140 weekly journals from both ends of two foster homes and one university. Eight subcategories (content and learning, practical learning, tutoring concerns, knowledge gains, competency gains, adult guidance, e-tutoring approaches, and transformative development) are categorized along with Ramsden’s hierarchy theory—teaching as telling or transmission, teaching as organizing student activity, and teaching as making learning possible. With transformative development of the campus-community partnership the consensus goal among university faculty, directors of foster homes and relevant personnel of e-tutoring (Enos and Morton 2003), the study discussed future improvements for the e-tutoring program. The action research strongly suggests that e-tutoring should emphasize more reflective listening rather than subject-mattered achievement and turn service-learning into an opportunity of achieving the sustainable integration of community resources and social welfare institutions.     

Necroptosis and ferroptosis are alternative cell death pathways that operate in acute kidney failure

Ferroptosis is a recently recognized caspase-independent form of regulated cell death that is characterized by the accumulation of lethal lipid ROS produced through iron-dependent lipid peroxidation. Considering that regulation of fatty acid metabolism is responsible for the membrane-resident pool of oxidizable fatty acids that undergo lipid peroxidation in ferroptotic processes, we examined the contribution of the key fatty acid metabolism enzyme, acyl-CoA synthetase long-chain family member 4 (ACSL4), in regulating ferroptosis. By using CRISPR/Cas9 technology, we found that knockout of Acsl4 in ferroptosis-sensitive murine and human cells conferred protection from erastin- and RSL3-induced cell death. In the same cell types, deletion of mixed lineage kinase domain-like (Mlkl) blocked susceptibility to necroptosis, as expected. Surprisingly, these studies also revealed ferroptosis and necroptosis are alternative, in that resistance to one pathway sensitized cells to death via the other pathway. These data suggest a mechanism by which one regulated necrosis pathway compensates for another when either ferroptosis or necroptosis is compromised. We verified the synergistic contributions of ferroptosis and necroptosis to tissue damage during acute organ failure in vivo. Interestingly, in the course of pathophysiological acute ischemic kidney injury, ACSL4 was initially upregulated and its expression level correlated with the severity of tissue damage. Together, our findings reveal ACSL4 to be a reliable biomarker of the emerging cell death modality of ferroptosis, which may also serve as a novel therapeutic target in preventing pathological cell death processes.     

Spectrin mutations cause spinocerebellar ataxia type 5

We have discovered that beta-III spectrin (SPTBN2) mutations cause spinocerebellar ataxia type 5 (SCA5) in an 11-generation American kindred descended from President Lincoln's grandparents and two additional families. Two families have separate in-frame deletions of 39 and 15 bp, and a third family has a mutation in the actin/ARP1 binding region. Beta-III spectrin is highly expressed in Purkinje cells and has been shown to stabilize the glutamate transporter EAAT4 at the surface of the plasma membrane. We found marked differences in EAAT4 and GluRdelta2 by protein blot and cell fractionation in SCA5 autopsy tissue. Cell culture studies demonstrate that wild-type but not mutant beta-III spectrin stabilizes EAAT4 at the plasma membrane. Spectrin mutations are a previously unknown cause of ataxia and neurodegenerative disease that affect membrane proteins involved in glutamate signaling.     

Localized maternal orthodenticle patterns anterior and posterior in the long germ wasp Nasonia

The Bicoid (Bcd) gradient in Drosophila has long been a model for the action of a morphogen in establishing embryonic polarity. However, it is now clear that bcd is a unique feature of higher Diptera. An evolutionarily ancient gene, orthodenticle (otd), has a bcd-like role in the beetle Tribolium. Unlike the Bcd gradient, which arises by diffusion of protein from an anteriorly localized messenger RNA, the Tribolium Otd gradient forms by translational repression of otd mRNA by a posteriorly localized factor. These differences in gradient formation are correlated with differences in modes of embryonic patterning. Drosophila uses long germ embryogenesis, where the embryo derives from the entire anterior-posterior axis, and all segments are patterned at the blastoderm stage, before gastrulation. In contrast, Tribolium undergoes short germ embryogenesis: the embryo arises from cells in the posterior of the egg, and only anterior segments are patterned at the blastoderm stage, with the remaining segments arising after gastrulation from a growth zone. Here we describe the role of otd in the long germband embryo of the wasp Nasonia vitripennis. We show that Nasonia otd maternal mRNA is localized at both poles of the embryo, and resulting protein gradients pattern both poles. Thus, localized Nasonia otd has two major roles that allow long germ development. It activates anterior targets at the anterior of the egg in a manner reminiscent of the Bcd gradient, and it is required for pre-gastrulation expression of posterior gap genes.     

Exploring biology with small organic molecules

Small organic molecules have proven to be invaluable tools for investigating biological systems, but there is still much to learn from their use. To discover and to use more effectively new chemical tools to understand biology, strategies are needed that allow us to systematically explore 'biological-activity space'. Such strategies involve analysing both protein binding of, and phenotypic responses to, small organic molecules. The mapping of biological-activity space using small molecules is akin to mapping the stars--uncharted territory is explored using a system of coordinates that describes where each new feature lies.     

Gene expression-based high-throughput screening(GE-HTS) and application to leukemia differentiation

Chemical genomics involves generating large collections of small molecules and using them to modulate cellular states. Despite recent progress in the systematic synthesis of structurally diverse compounds, their use in screens of cellular circuitry is still an ad hoc process. Here, we outline a general, efficient approach called gene expression-based high-throughput screening (GE-HTS) in which a gene expression signature is used as a surrogate for cellular states, and we describe its application in a particular setting: the identification of compounds that induce the differentiation of acute myeloid leukemia cells. In screening 1,739 compounds, we identified 8 that reliably induced the differentiation signature and, furthermore, yielded functional evidence of bona fide differentiation. The results indicate that GE-HTS may be a powerful, general approach for chemical screening.