Live-cell imaging reveals subcellular localization of plant membrane compartments during oomycete infections and quantitative high-throughput imaging identifies endocytic trafficking mutants

To successfully infect plants, filamentous pathogens such as the oomycete Hyaloperonospora arabidopsidis (Hpa) are able to penetrate host tissues and form haustoria, a feeding structure, inside the host cell. Reorganization of the host cell is required to accommodate the haustoria. Formation of haustoria is accompanied by the biogenesis of the extrahaustorial membrane (EHM) which surrounds the haustorium and separates the host cell from the pathogen. In this study, available fluorescent marker protein fusions were used to monitor the re-distribution of membrane compartments at the interface between Arabidopsis and Hpa. The aquaporin PIP1;4, the ATPase ACA8, and the plasma membrane (PM) intrinsic protein NPSN12 were excluded from the EHM while the syntaxin PEN1 and the receptor-like kinase FLS2 labelled the EHM. This suggests PM-resident proteins are recruited to the EHM selectively. The nucleus is always observed adjacent to haustoria, suggesting that the presence of haustoria causes migration of the nucleus. Secretory vesicles and endosomal compartments localize around the haustoria, implicating secretory and endocytic pathways in the biogenesis of the EHM. Upon Hpa infection, haustorial encasements develop around mature haustoria. All examined plant proteins accumulate at haustorial encasements, indicating that formation of encasements is derived by default redirection of vesicle trafficking pathways. With the aim to genetically dissect endosomal trafficking regulators, I took advantage of quantitative high throughput confocal imaging system and transgenic plants containing the fluorescent biosensor GFP-2xFYVE to perform a forward genetic screen. Different numbers of GFP-2xFYVE positive endosomes were found in two reference lines, Ler/GFP-2xFYVE and Col-0/YFP-2xFYVE suggesting the endosomal levels may vary in different ecotypes of Arabidopsis. Mutants with altered numbers of FYVE Endosomal Levels (fel) have been previous identified and were re-confirmed in this study. fel1, fel2, fel3, fel6, fel9, and fel12 revealed genetically recessive mutations while fel10 could not reveal its genetic inheritance. Two mutants, fel2 and fel9 exhibited more GFP-2xFYVE compartments than wild-type reference plants. These two mutants are affected in endosome trafficking and fel2 is likely tissue specific. We identified gene loci by classical mapping and whole genome sequencing. Fel2 co-segregated with the lower arm of chromosome 4. Fel9 was mapped to two chromosome loci. Investigation of genes in the rough mapping region will unravel regulators of endocytosis or multivesicular bodies (MVBs) biogenesis. Because only few mutant phenotypes recovered in the F2 of backcrossed fel2 and fel9, identification of FEL2 and FEL9 was hampered. Additionally, basal differences of endosomal numbers in the reference lines lead to the limitation for genetic screen based on quantitative changes in endosomal numbers. Altogether, these results show that there are common elements in the subcellular changes associated with biotrophic oomycete between different pathogens. For Hpa and other fungal/oomycete pathogens, reprogramming host cell vesicle trafficking occurs to accommodate haustorial structures. A genetic screen for novel endocytosis mutants, based on quantitative measurements of endosomal numbers, was performed with advanced microscopy technology. Fel mutant plants may be further used to study molecular mechanisms for membrane trafficking, as well as subcellular rearrangement in plant-pathogen interactions

Interface control of ferroelectricity in LaNiO3-BaTiO3 superlattices

LaNiO$_{3}$-BaTiO$_{3}$ superlattices with different types of interfaces are studied from first-principles density-functional theory. It is revealed that the ferroelectricity in the superlattice with (NiO$_2$)$^-$/(BaO)$^0$ interfaces is enhanced from that of the superlattice with (LaO)$^+$/(TiO$_2$)$^0$ interfaces. The origin lies at the polar discontinuity at the interface, which makes the holes localized within the (NiO$_2$)$^-$/(BaO)$^0$ interface, but drives a penetration of electrons into BaTiO$_3$ component near (LaO)$^+$/(TiO$_2$)$^0$ interface. Our calculations demonstrate an effective avenue to the robust ferroelectricity in BaTiO$_3$ ultrathin films.Comment: 14 pages, 6 figure

Shakura-Sunyaev Disk Can Smoothly Match Advection-Dominated Accretion Flow

We use the standard Runge-Kutta method to solve the set of basic equations describing black hole accretion flows composed of two-temperature plasma. We do not invoke any extra energy transport mechanism such as thermal conduction and do not specify any ad hoc outer boundary condition for the advection-dominated accretion flow (ADAF) solution. We find that in the case of high viscosity and non-zero radiative cooling, the ADAF solution can have an asymptotic approach to the Shakura-Sunyaev disk (SSD) solution, and the SSD-ADAF transition radius is close to the central black hole. Our results further prove the mechanism of thermal instability-triggered SSD-ADAF transition suggested previously by Takeuchi & Mineshige and Gu & Lu.Comment: 10 pages, 2 figures, accepted for publication in ApJ Letter

Effects of ranibizumab on human corneal endothelial cells

AbstractPurposeThis study aims to evaluate corneal endothelial changes occurring over a 3-month period after intravitreal injections of ranibizumab in patients with wet age-related macular degeneration.MethodsThis is a prospective case series. A total of 29 patients (29 eyes) received a 0.5-mg intravitreal injection of ranibizumab. Specular microscopy, including measurement of central corneal thickness and endothelial cell count, was performed on each patient prior to and after completing three intravitreal injections.ResultsAll patients received three intravitreal injections and were followed up for a mean of 3 months. There was no significant change in corneal thickness (p = 0.32) or endothelial cell density (p = 0.38) after ranibizumab injections.ConclusionIntravitreal ranibizumab injections (0.5 mg) have no harmful effects on corneal endothelial cells