Cytoplasmic continuity revisited: closure of septa of the filamentous fungus Schizophyllum commune in response to environmental conditions

Background: Mycelia of higher fungi consist of interconnected hyphae that are compartmentalized by septa. These septa contain large pores that allow streaming of cytoplasm and even organelles. The cytoplasm of such mycelia is therefore considered to be continuous.Methodology/Principal Findings: Here, we show by laser dissection that septa of Schizophyllum commune can be closed depending on the environmental conditions. The most apical septum of growing hyphae was open when this basidiomycete was grown in minimal medium with glucose as a carbon source. In contrast, the second and the third septum were closed in more than 50% and 90% of the cases, respectively. Interestingly, only 24 and 37% of these septa were closed when hyphae were growing in the absence of glucose. Whether a septum was open or closed also depended on physical conditions of the environment or the presence of toxic agents. The first septum closed when hyphae were exposed to high temperature, to hypertonic conditions, or to the antibiotic nourseothricin. In the case of high temperature, septa opened again when the mycelium was placed back to the normal growth temperature.Conclusions/Significance: Taken together, it is concluded that the septal pores of S. commune are dynamic structures that open or close depending on the environmental conditions. Our findings imply that the cytoplasm in the mycelium of a higher fungus is not continuous perse

The <i>Ectocarpus</i> genome and the independent evolution of multicellularity in brown algae

Brown algae (Phaeophyceae) are complex photosynthetic organisms with a very different evolutionary history to green plants, to which they are only distantly related1. These seaweeds are the dominant species in rocky coastal ecosystems and they exhibit many interesting adaptations to these, often harsh, environments. Brown algae are also one of only a small number of eukaryotic lineages that have evolved complex multicellularity (Fig. 1).We report the 214 million base pair (Mbp) genome sequence of the filamentous seaweed Ectocarpus siliculosus (Dillwyn) Lyngbye, a model organism for brown algae, closely related to the kelps (Fig. 1). Genome features such as the presence of an extended set of light-harvesting and pigment biosynthesis genes and new metabolic processes such as halide metabolism help explain the ability of this organism to cope with the highly variable tidal environment. The evolution of multicellularity in this lineage is correlated with the presence of a rich array of signal transduction genes. Of particular interest is the presence of a family of receptor kinases, as the independent evolution of related molecules has been linked with the emergence of multicellularity in both the animal and green plant lineages. The Ectocarpus genome sequence represents an important step towards developing this organism as a model species, providing the possibility to combine genomic and genetic2 approaches to explore these and other aspects of brown algal biology further

Repositioning of the global epicentre of non-optimal cholesterol

High blood cholesterol is typically considered a feature of wealthy western countries1,2. However, dietary and behavioural determinants of blood cholesterol are changing rapidly throughout the world3 and countries are using lipid-lowering medications at varying rates. These changes can have distinct effects on the levels of high-density lipoprotein (HDL) cholesterol and non-HDL cholesterol, which have different effects on human health4,5. However, the trends of HDL and non-HDL cholesterol levels over time have not been previously reported in a global analysis. Here we pooled 1,127 population-based studies that measured blood lipids in 102.6 million individuals aged 18 years and older to estimate trends from 1980 to 2018 in mean total, non-HDL and HDL cholesterol levels for 200 countries. Globally, there was little change in total or non-HDL cholesterol from 1980 to 2018. This was a net effect of increases in low- and middle-income countries, especially in east and southeast Asia, and decreases in high-income western countries, especially those in northwestern Europe, and in central and eastern Europe. As a result, countries with the highest level of non-HDL cholesterol—which is a marker of cardiovascular risk—changed from those in western Europe such as Belgium, Finland, Greenland, Iceland, Norway, Sweden, Switzerland and Malta in 1980 to those in Asia and the Pacific, such as Tokelau, Malaysia, The Philippines and Thailand. In 2017, high non-HDL cholesterol was responsible for an estimated 3.9 million (95% credible interval 3.7 million–4.2 million) worldwide deaths, half of which occurred in east, southeast and south Asia. The global repositioning of lipid-related risk, with non-optimal cholesterol shifting from a distinct feature of high-income countries in northwestern Europe, north America and Australasia to one that affects countries in east and southeast Asia and Oceania should motivate the use of population-based policies and personal interventions to improve nutrition and enhance access to treatment throughout the world.</p

Repositioning of the global epicentre of non-optimal cholesterol

High blood cholesterol is typically considered a feature of wealthy western countries1,2. However, dietary and behavioural determinants of blood cholesterol are changing rapidly throughout the world3 and countries are using lipid-lowering medications at varying rates. These changes can have distinct effects on the levels of high-density lipoprotein (HDL) cholesterol and non-HDL cholesterol, which have different effects on human health4,5. However, the trends of HDL and non-HDL cholesterol levels over time have not been previously reported in a global analysis. Here we pooled 1,127 population-based studies that measured blood lipids in 102.6 million individuals aged 18 years and older to estimate trends from 1980 to 2018 in mean total, non-HDL and HDL cholesterol levels for 200 countries. Globally, there was little change in total or non-HDL cholesterol from 1980 to 2018. This was a net effect of increases in low- and middle-income countries, especially in east and southeast Asia, and decreases in high-income western countries, especially those in northwestern Europe, and in central and eastern Europe. As a result, countries with the highest level of non-HDL cholesterol�which is a marker of cardiovascular risk�changed from those in western Europe such as Belgium, Finland, Greenland, Iceland, Norway, Sweden, Switzerland and Malta in 1980 to those in Asia and the Pacific, such as Tokelau, Malaysia, The Philippines and Thailand. In 2017, high non-HDL cholesterol was responsible for an estimated 3.9 million (95 credible interval 3.7 million�4.2 million) worldwide deaths, half of which occurred in east, southeast and south Asia. The global repositioning of lipid-related risk, with non-optimal cholesterol shifting from a distinct feature of high-income countries in northwestern Europe, north America and Australasia to one that affects countries in east and southeast Asia and Oceania should motivate the use of population-based policies and personal interventions to improve nutrition and enhance access to treatment throughout the world. © 2020, The Author(s), under exclusive licence to Springer Nature Limited

Rising rural body-mass index is the main driver of the global obesity epidemic in adults

Body-mass index (BMI) has increased steadily in most countries in parallel with a rise in the proportion of the population who live in cities 1,2 . This has led to a widely reported view that urbanization is one of the most important drivers of the global rise in obesity 3�6 . Here we use 2,009 population-based studies, with measurements of height and weight in more than 112 million adults, to report national, regional and global trends in mean BMI segregated by place of residence (a rural or urban area) from 1985 to 2017. We show that, contrary to the dominant paradigm, more than 55 of the global rise in mean BMI from 1985 to 2017�and more than 80 in some low- and middle-income regions�was due to increases in BMI in rural areas. This large contribution stems from the fact that, with the exception of women in sub-Saharan Africa, BMI is increasing at the same rate or faster in rural areas than in cities in low- and middle-income regions. These trends have in turn resulted in a closing�and in some countries reversal�of the gap in BMI between urban and rural areas in low- and middle-income countries, especially for women. In high-income and industrialized countries, we noted a persistently higher rural BMI, especially for women. There is an urgent need for an integrated approach to rural nutrition that enhances financial and physical access to healthy foods, to avoid replacing the rural undernutrition disadvantage in poor countries with a more general malnutrition disadvantage that entails excessive consumption of low-quality calories. © 2019, The Author(s)

Structure and function of the septal pore cap of Schizophyllum commune

Filamentous fungi form networks (mycelia) of long, tubular structures (hyphae) that extend at their tip (apex) and branch subapically (behind the tip). Hyphae are compartmentalized by cross walls (septa) that contain a central pore which is covered by a septal pore cap (SPC) in fungi belonging to the Basidiomycetes. In this thesis I studied the composition and function of the SPC of S. commune. SPCs were purified and their composition, proteins and corresponding genes were identified. Analysis of genes of the SPC was combined with improvement of methods for transformation and gene inactivation. Finally, I developed a method to study septa in the mycelium under stress. SPCs of S. commune were purified by separating homogenized mycelium containing 1 % Triton-X-100 on two discontinuous sucrose gradients, followed by filtration over a membrane. The SPC is composed of a proteinaceous core surrounded by membranous material. We show that this core determines the shape of the SPC and consists of two abundant proteins; SPC14 and SPC33. The SPC14 gene encodes a protein of 86 amino acids without known signal or signature sequences. Expressed sequence tag (EST) analysis indicates that SPC33 encodes a 239 and 340 amino acid variant that share a predicted signal anchor, a putative RXR ER localization signal, and a transmembrane region. SPC14 and SPC33 are only found in basidiomycetes with a SPC. Presence of SPC14 and SPC33 in the SPC was confirmed by immuno-localization. Previously, S. commune was transformed to phleomycin resistance using the ble gene of Streptoalloteychus hindustanus. I show that selective concentrations of phleomycin are mutagenic to resistant strains. Therefore, a nourseothricin resistance cassette was constructed with the nat1 gene of Streptomyces noursei. Transformation efficiency with nourseothricin was ten-fold lower, but could be restored by adding phleomycin which was accompanied by an increase of single copy integrations. The nourseothricin and phleomycin cassette were used to construct a vector for rapid screening of homologous integrations and was successfully applied for gene deletions in our lab. However, out of 800 transformants none showed inactivation of the SPC14 or SPC33 gene. Therefore, they might be essential, which is supported by the fact that RNA interference of the SPC14 gene was unstable. Reduced SPC14 mRNA levels, seemingly correlating with reduced growth in monokaryons and abnormal fruiting in dikaryons, was lost upon transfer to fresh medium. Using laser dissection it was assessed whether septa in a mycelium are open or closed. I showed that the apical septum is always open, the second septum is sometimes closed and the third septum is in most cases closed. Upon exposure to antibiotic, heat stress, or hypertonic conditions the first septum closes. The observed plugging mechanism seems to be an emergency response since arrest of growth and vacuolization of cytoplasm precede septal closure. Heat-induced closure was reversible, which indicates that septa are dynamic structures. Apical compartments were found to be able to reinitiate growth after separation from the mycelium. The fact that the third septum is mostly closed challenges the general assumption that mycelia are continuous systems

First report of Podosphaera xanthii causing powdery mildew on Ageratum conyzoides in China

Ageratum conyzoides L. is a member of the Asteraceae and a competitive weed for crops in the subtropics and tropics. In September 2016, we observed that a plant community of A. conyzoides was 85% infected with powdery mildew in a forest park at Fujian Agriculture and Forestry University (FAFU), Fuzhou, China. Initially, circular to irregular white powdery colonies or thinly effuse white mycelial patches formed on both sides of the leaves and on the stems. In later stages, entire leaves were covered with white mycelium, followed by leaf yellowing and senescence. Fungal hyphae were septate, branched, flexuous to straight, and 5 to 7 μm wide. Appressoria were indistinct to slightly nipple-shaped and solitary. Conidiophores (80 to 215 × 10 to 12 μm) were erect and unbranched, slightly constricted at the basal septa, with cylindrical foot-cells (35 to 70 × 10 to 12 µm) and 1 to 3 cells shorter than the foot-cell. Conidia (25 to 40 × 14 to 23 μm) were hyaline, catenescent, ellipsoid-ovoid to barrel-shaped, with a length/width ratio of 1.3 to 2.0, and containing distinct fibrosin bodies. Simple to forked germ tubes were observed on subterminal or lateral position of germinating conidia. No chasmothecia were observed in the collected infected samples. Based on the morphology of the imperfect state, the isolate was identified as Podosphaera xanthii (Castagne) U. Braun & N. Shishkoff (Braun and Cook 2012). A 565-bp amplicon (KY274485) of the internal transcribed spacer (ITS) region generated with primers ITS1/ITS4 (White et al. 1990) was 100% identical with other P. xanthii sequences (AB040351, AB462804) and showed phylogenetic grouping with P. xanthii isolates from Asteraceae and Verbenaceae. Pathogenicity tests were completed by dusting conidia from an infected leaf onto young leaves of three asymptomatic, potted plants and covered with plastic bags. Noninoculated plants were used as controls. Inoculated leaves showed powdery mildew symptoms after 6 days at 20°C and 80% relative humidity in green house. Control plants exhibited no disease symptoms. The fungal morphology on inoculated leaves was identical to that observed on initially diseased leaves. A voucher specimen (HMAS 247182) was deposited in Institute of Microbiology Chinese Academy of Sciences (CAS) Herbarium Mycologium (HMAS), Beijing, China. Previously, Euoidium agerati has been mentioned as powdery mildew pathogen on A. conyzoides in Taiwan (Braun and Cook 2012). However, this pathogen is quite different from the present collection by not having fibrosin bodies in conidia. Powdery mildew of A. conyzoides caused by P. xanthii has been recorded in Pakistan and India (Gautam 2015; Mukhtar et al. 2013). In China, A. conyzoides is used as medicinal plant to treat a variety of conditions and diseases. Incidence of P. xanthii on this plant will add information on pathogen’s range and will be helpful for future investigation. To our knowledge, this is the first report of P. xanthii on A. conyzoides in China

First report of powdery mildew caused by Podosphaera xanthii on Euphorbia hirta in China

Euphorbia hirta is an important medicinal herb that can be found on grassland, roadsides, and field pathways in tropical regions of world. In late October and early November 2016, powdery mildew was observed on E. hirta growing along roadsides in Fujian Agriculture and Forestry University (26°5’16”N, 119°14’6”E), Fuzhou, China. Disease incidence approached 100%, with fungal colonies present on stems and both sides of the leaves. At the initial stages of infection, colonies were circular to irregular and later covered the entire leaf surface. Hyphae were septated, branched, flexuous to straight, up to 8 μm wide with indistinct to slightly nipple-shaped appressoria. Conidiophores were unbranched, straight, 90 to 260 × 10 to 13 μm in size. Foot-cells of the conidiophores were cylindrical, 40 to 80 μm long, with slight constriction at basal septa, and followed by 1 to 3 short cells. Conidia were hyaline, formed in chains of 2 to 6 cells with distinct fibrosin bodies visible in their cytoplasm, ellipsoid-ovoid to barrel-shaped, about 30 to 45 × 14 to 20 μm in size, with a length to width ratio of mostly 1.5 to 2.0. Chasmothecia were absent. The rDNA internal transcribed spacer (ITS) region was amplified from pools of conidia on infected leaves by using primers ITS1/ITS4 (†) and directly sequenced. BLASTn analysis of the 569 bp (KY388504) amplicon revealed 100% sequence identity with respective rDNA sequences of Podosphaera xanthii isolates from Asteraceae (Bidens pilosa [KM260740], Youngia denticulata [AB040351]), Euphorbiaceae (Euphorbia thymifolia [KM260731]), Solanaceae (Physalis angulata [KM260744]), and Verbenaceae (Verbena brasiliensis [KJ472787]). Phylogenetic analysis also indicated clustering of E. hirta fungal isolate with P. xanthii strains. Based on the morphological characteristics and ITS sequences, the fungal species was identified as P. xanthii (Castagne) U. Braun & Shiskoff (†). Pathogenicity of the fungal isolate was confirmed by gently pressing diseased leaves onto the leaves of three healthy E. hirta plants, resulting in the formation of white powdery mildew colonies after 7 days at 20°C and 80% relative humidity in a greenhouse. Fungal colonies on the inoculated plants were morphologically identical to the collected fungal specimen, whereas control plants of E. hirta developed no symptoms of powdery mildew. Until now, P. euphorbiae-hirtae was documented on E. hirta, E. tithymaloides, and A. australis (†;†). However, recently Golovinomyces orontii has also been reported on E. hirta in India (†). E. hirta is an important medicinal plant in China and present information will be helpful in understanding the range of pathogen that can infect this plant. To our knowledge, this is the first report of P. xanthii on E. hirta