Mechanistic and genetic basis of single-strand templated repair at Cas12a-induced DNA breaks in Chlamydomonas reinhardtii

Single-stranded oligodeoxynucleotides (ssODNs) are widely used as DNA repair templates inCRISPR/Cas precision genome editing. However, the underlying mechanisms of single-strandtemplated DNA repair (SSTR) are inadequately understood, constraining rational improve-ments to precision editing. Here we study SSTR at CRISPR/Cas12a-induced DNA double-strand breaks (DSBs) in the eukaryotic model green microalgaChlamydomonas reinhardtii.Wedemonstrate that ssODNs physically incorporate into the genome during SSTR at Cas12a-induced DSBs. This process is genetically independent of the Rad51-dependent homologousrecombination and Fanconi anemia pathways, is strongly antagonized by non-homologousend-joining, and is mediated almost entirely by the alternative end-joining enzyme poly-meraseθ. Thesefindings suggest differences in SSTR betweenC. reinhardtiiand animals. Ourwork illustrates the promising potentially ofC. reinhardtiias a model organism for studyingnuclear DNA repair

Environmental morphing enables informed dispersal of the dandelion diaspore

Animal migration is highly sensitised to environmental cues, but plant dispersal is considered largely passive. The common dandelion, Taraxacum officinale, bears an intricate haired pappus facilitating flight. The pappus enables the formation of a separated vortex ring during flight; however, the pappus structure is not static but reversibly changes shape by closing in response to moisture. We hypothesised that this leads to changed dispersal properties in response to environmental conditions. Using wind tunnel experiments for flow visualisation, particle image velocimetry, and flight tests we characterised the fluid mechanics effects of the pappus morphing. We also modelled dispersal to understand the impact of pappus morphing on diaspore distribution. Pappus morphing dramatically alters the fluid mechanics of diaspore flight. We found that when the pappus closes in moist conditions, the drag coefficient decreases and thus the falling velocity is greatly increased. Detachment of diaspores from the parent plant also substantially decreases. The change in detachment when the pappus closes increases dispersal distances by reducing diaspore release when wind speeds are low. We propose that moisture-dependent pappus-morphing is a form of informed dispersal allowing rapid responses to changing conditions

A bottom-up view of food surplus: using stable carbon and nitrogen isotope analysis to investigate agricultural strategies and diet at Bronze Age Archontiko and Thessaloniki Toumba, northern Greece

We use stable isotope analysis of crop, faunal and human remains to investigate agricultural strategies and diet at EBA-LBA Archontiko and MBA-LBA Thessaloniki Toumba. Crop production strategies varied between settlements, phases and species; flexibility is also apparent within the crop stores of individual houses. Escalating manuring intensity at LBA Thessaloniki Toumba coincides with large co-residential ‘blocks’ geared towards hoarding of agricultural surpluses, spectacularly preserved by fire at nearby LBA Assiros Toumba. Faunal isotope values reflect a range of feeding strategies, including probable herding of cattle on C4-rich coastal salt marshes, evident at Archontiko through to the LBA alongside bulk cockle harvesting. Palaeodietary analysis of LBA humans at Thessaloniki Toumba indicates that C3 crops represent the only plausible staples. Millet was a minor food but may have played a particular role in the sub-adult diet. Meat probably featured in supra-household food sharing and hospitality, associated with Mycenaean-style tableware in the LBA

The Double Bind of Black Manhood : The Language of Masculinity in African American Writings, 1800-1900

This dissertation describes the contested vision of African American masculinity in the work of 19th century abolitionists, African American activists, and Southern slaveholders. My project looks at the social and political battle over the meaning of African American masculinity from 1800 until 1900 through works of literature written by such authors as David Walker, William Whipper, Frederick Douglass, Harriet Beecher Stowe, Charles Chesnutt and Albion Turgée. In these texts, African American men participated in both self-fashioning and the performance of various visions of manhood while contending with the conditions created by both pro-slavery depictions of black inhumanity and abolitionist renderings of black victimhood

M1 Protein-Dependent Intracellular Trafficking Promotes Persistence and Replication of Streptococcus pyogenes in Macrophages

Streptococcus pyogenes is an important human pathogen that causes a variety of diseases including life-threatening invasive diseases, such as toxic shock and deep tissue infections. Although S. pyogenes are classically considered extracellular pathogens, a clinical significance of an intracellular source has been emphasized. In patients with deep tissue infections, an intracellular reservoir of S. pyogenes within macrophages was shown to contribute to prolonged bacterial persistence. Here we demonstrate that intracellular survival of S. pyogenes in macrophages is associated with an M1 protein-dependent intracellular trafficking in the phagosomal-lysosomal pathway, which results in impaired fusion with lysosomes. The phagocytic vacuoles harbouring M1 protein-expressing bacteria not only served as a safe haven for the bacteria, but also as a replicating niche. An M1 protein-dependent modulation of macrophages was further supported by differences in NF-kappa B signalling between cells infected with either the wild-type or M1 protein-deficient strains, thereby indicating a suppressed inflammatory response when M1 protein was involved. Evidence of egress of bacteria out of their host cell and subsequent re-infection of new cells emphasize the importance of intracellular bacteria as a reservoir for dissemination of infection and continued tissue injury. Copyright (C) 2010 S. Karger AG, Base

Informed dispersal of the dandelion

Long distance dispersal (LDD) is considered particularly important for plant range expansion (1). Such events are rare, however, and for wind-dispersed species updrafts or extreme weather events are required (1–3). Despite the importance of LDD for plant population dynamics, dispersing long distances is risky to the survival of individual seeds and the majority of seeds disperse short distances. The extent to which most wind dispersed plants can manipulate dispersal ranges of individual seeds is debatable as wind speeds are generally more variable than seed traits (4–9). Here, we present a dynamic mechanism by which dandelion (Taraxacum officinale) seeds can regulate their dispersal in response to environmental conditions. We used time lapse imaging to observe shape changes in dandelion pappi. We also analysed diaspore fluid mechanics in two wind tunnels and used particle image velocimetry (PIV) to understand flight characteristics of the morphing structure. We have found that by changing the shape of the pappus when wet, detachment from the parent plant is greatly reduced and seed falling velocities are increased with a significant change in velocity deficit behind the seed. We suggest that this may be a form of informed dispersal maintaining LDD in dry conditions, while spatiotemporally directing short-range dispersal toward beneficial wetter environments