Comprehensive mapping of mutations in the SARS-CoV-2 receptor-binding domain that affect recognition by polyclonal human plasma antibodies

1. Download : Download high-res image (199KB)
2. Download : Download full-size image

     

Ethylene-induced growth and proton excretion in the aquatic plant Nymphoides peltata

In the presence of auxin, ethylene can promote growth in petioles of N. peltata (S.G. Gmel.) O. Kuntze. Acid buffer will also stimulate growth in the tissue and, in abraded petiole segments, ethylene-stimulated growth is accompanied by a marked acidification of the medium. Auxin stimulates growth in this tissue and, for various auxin and ethylene treatments, the amount of growth is closely correlated with the degree of medium acidification. The results are consistent with predictions of the ‘acid-growth’ theory, and provide the first evidence that ethylene acts by an ‘acid-growth’ mechanism.     

Trehalose and α-glucan mediate distinct abiotic stress responses in Pseudomonas aeruginosa

An important prelude to bacterial infection is the ability of a pathogen to survive independently of the host and to withstand environmental stress. The compatible solute trehalose has previously been connected with diverse abiotic stress tolerances, particularly osmotic shock. In this study, we combine molecular biology and biochemistry to dissect the trehalose metabolic network in the opportunistic human pathogen Pseudomonas aeruginosa PAO1 and define its role in abiotic stress protection. We show that trehalose metabolism in PAO1 is integrated with the biosynthesis of branched α-glucan (glycogen), with mutants in either biosynthetic pathway significantly compromised for survival on abiotic surfaces. While both trehalose and α-glucan are important for abiotic stress tolerance, we show they counter distinct stresses. Trehalose is important for the PAO1 osmotic stress response, with trehalose synthesis mutants displaying severely compromised growth in elevated salt conditions. However, trehalose does not contribute directly to the PAO1 desiccation response. Rather, desiccation tolerance is mediated directly by GlgE-derived α-glucan, with deletion of the glgE synthase gene compromising PAO1 survival in low humidity but having little effect on osmotic sensitivity. Desiccation tolerance is independent of trehalose concentration, marking a clear distinction between the roles of these two molecules in mediating responses to abiotic stress.