African origin and global distribution patterns: Evidence inferred from phylogenetic and biogeographical analyses of ectomycorrhizal fungal genus Strobilomyces

Aim

The ectomycorrhizal genus Strobilomyces is widely distributed throughout many parts of the world, but its origin, divergence and distribution patterns remain largely unresolved. In this study, we aim to explore the species diversity, distribution and evolutionary patterns of Strobilomyces on a global scale by establishing a general phylogenetic framework with extensive sampling.

Location

Africa, Australasia, East Asia, Europe, North America, Central America and Southeast Asia.

Methods

The genealogical concordance phylogenetic species recognition method was used to delimit phylogenetic species. Divergence times were estimated using a Bayesian uncorrelated lognormal relaxed molecular clock. The ancestral area and host of Strobilomyces were inferred via the programs rasp and mesquite . The change of diversification rate over time was estimated using Ape, Laser and Bammtools software packages.

Results

We recognize a novel African clade and 49 phylogenetic species with morphological evidence, including 18 new phylogenetic species and 23 previously described ones. Strobilomyces probably originated in Africa, in association with Detarioideae/Phyllanthaceae/Monotoideae during the early Eocene. The dispersal to Southeast Asia can be explained by Wolfe's “Boreotropical migration” hypothesis. East Asia, Australasia, Europe and North/Central America are primarily the recipients of immigrant taxa during the Oligocene or later. A rapid radiation implied by one diversification shift was inferred within Strobilomyces during the Miocene.

Main conclusions

An unexpected phylogenetic species diversity within Strobilomyces was uncovered. The highest diversity, resulting probably from a rapid radiation, was found in East Asia. Dispersal played an important role in the current distribution pattern of Strobilomyces. The Palaeotropical disjunction is explained by species dispersal from Africa to Southeast Asia through boreotropical forests during the early Eocene. Species from the Northern Hemisphere and Australasia are largely derived from immigrant ancestors from Southeast Asia.     

Genetic diversity and relationship of Fritillaria thunbergii Miq. landraces and related taxa

Genetic diversity and differentiation of four landraces of Fritillaria thunbergii Miq. and two congeners Fritillaria cirrhosa D. Don and Fritillaria anhuiensis S. C. Chen et S. F. Yin were evaluated using ISSR markers. The results showed that the genetic diversity of F. thunbergii was high at the specie level but relatively lower at the landrace level. A high level of genetic differentiation among four F. thunbergii landraces was detected based on the gene differentiation coefficient and the AMOVA, in line with the low inter-landrace gene flow. MS-tree analysis showed that the four F. thunbergii landraces were clustered on adjacent positions of the tree, and that Kuanye (Ft-KY) landrace was relatively distantly related to other landraces. In line with the MS-tree analysis, PCoA revealed that the three species of Fritillaria can be divided into two groups and three subgroups, among which there occurred a remarkable genetic differentiation.     

Engineering of Acetate Recycling and Citrate Synthase to Improve Aerobic Succinate Production in Corynebacterium glutamicum

Corynebacterium glutamicum lacking the succinate dehydrogenase complex can produce succinate aerobically with acetate representing the major byproduct. Efforts to increase succinate production involved deletion of acetate formation pathways and overexpression of anaplerotic pathways, but acetate formation could not be completely eliminated. To address this issue, we constructed a pathway for recycling wasted carbon in succinate-producing C. glutamicum. The acetyl-CoA synthetase from Bacillus subtilis was heterologously introduced into C. glutamicum for the first time. The engineered strain ZX1 (pEacsA) did not secrete acetate and produced succinate with a yield of 0.50 mol (mol glucose)⁻¹. Moreover, in order to drive more carbon towards succinate biosynthesis, the native citrate synthase encoded by gltA was overexpressed, leading to strain ZX1 (pEacsAgltA), which showed a 22% increase in succinate yield and a 62% decrease in pyruvate yield compared to strain ZX1 (pEacsA). In fed-batch cultivations, strain ZX1 (pEacsAgltA) produced 241 mM succinate with an average volumetric productivity of 3.55 mM h⁻¹ and an average yield of 0.63 mol (mol glucose) ⁻¹, making it a promising platform for the aerobic production of succinate at large scale.     

HIV Infection and Awareness among Men Who Have Sex with Men–20 Cities,United States, 2008 and 2011

Over half of HIV infections in the United States occur among men who have sex with men (MSM). Awareness of infection is a necessary precursor to antiretroviral treatment and risk reduction among HIV-infected persons. We report data on prevalence and awareness of HIV infection among MSM in 2008 and 2011, using data from 20 cities participating in the 2008 and 2011 National HIV Behavioral Surveillance System (NHBS) among MSM. Venue-based, time-space sampling was used to recruit men for interview and HIV testing. We analyzed data for men who reported ≥1 male sex partner in the past 12 months. Participants who tested positive were considered to be aware of their infection if they reported a prior positive HIV test. We used multivariable analysis to examine differences between results from 2011 vs. 2008. HIV prevalence was 19% in 2008 and 18% in 2011 (p = 0.14). In both years, HIV prevalence was highest among older age groups, blacks, and men with lower education and income. In multivariable analysis, HIV prevalence did not change significantly from 2008 to 2011 overall (p = 0.51) or in any age or racial/ethnic category (p>0.15 in each category). Among those testing positive, a greater proportion was aware of their infection in 2011 (66%) than in 2008 (56%) (p<0.001). In both years, HIV awareness was higher for older age groups, whites, and men with higher education and income. In multivariable analysis, HIV awareness increased from 2008 to 2011 overall (p<0.001) and for all age and racial/ethnic categories (p<0.01 in each category). In both years, black MSM had the highest HIV prevalence and the lowest awareness among racial/ethnic groups. These findings suggest that HIV-positive MSM are increasingly aware of their infections.     

Microtubule-assisted mechanism for toxisome assembly in Fusarium graminearum

In Fusarium graminearum, a trichothecene biosynthetic complex known as the toxisome forms ovoid and spherical structures in the remodelled endoplasmic reticulum (ER) under mycotoxin-inducing conditions. Previous studies also demonstrated that disruption of actin and tubulin results in a significant decrease in deoxynivalenol (DON) biosynthesis in F. graminearum. However, the functional association between the toxisome and microtubule components has not been clearly defined. In this study we tested the hypothesis that the microtubule network provides key support for toxisome assembly and thus facilitates DON biosynthesis. Through fluorescent live cell imaging, knockout mutant generation, and protein–protein interaction assays, we determined that two of the four F. graminearum tubulins, α₁ and β₂ tubulins, are indispensable for DON production. We also showed that these two tubulins are directly associated. When the α₁–β₂ tubulin heterodimer is disrupted, the metabolic activity of the toxisome is significantly suppressed, which leads to significant DON biosynthesis impairment. Similar phenotypic outcomes were shown when F. graminearum wild type was treated with carbendazim, a fungicide that binds to microtubules and disrupts spindle formation. Based on our results, we propose a model where α₁–β₂ tubulin heterodimer serves as the scaffold for functional toxisome assembly in F. graminearum.     

Recombinant platelet-derived growth factor-BB alleviates osteoarthritis in a rat model by decreasing chondrocyte apoptosis in vitro and in vivo

Osteoarthritis (OA) is a common joint disease that mainly affects the diarthrodial joints. Treatments for OA include non-pharmacological interventions, topical and oral therapies, intra-articular therapies and joint surgery. However, all the treatments mentioned above mainly aim to control the symptoms instead of improving or reversing the joint condition. In this research, we observed the effect of recombinant platelet-derived growth factor (PDGF)-BB on OA in a monosodium iodoacetate (MIA)–induced rat model and revealed the possible mechanisms. In vitro, the level of inflammation in the chondrocytes was gradually alleviated, and the apoptosis rate was gradually decreased by PDGF-BB at increasing concentrations. The levels of p-p38, Bax and caspase-3 decreased, and the level of p-Erk increased with increasing PDGF-BB concentration. In vivo, PDGF-BB could significantly reverse chondrocyte and matrix loss. Furthermore, high concentrations of PDGF-BB could alleviate cartilage hyperplasia to remodel the tissue. The level of collagen II was up-regulated, and the levels of collagen X and apoptosis were down-regulated by increasing concentrations of PDGF-BB. In conclusion, recombinant PDGF-BB alleviated OA by down-regulating caspase-3-dependent apoptosis. The effects of PDGF-BB on OA mainly include inhibiting chondrocyte loss, reducing cartilage hyperplasia and osteophyte formation, and regulating collagen anabolism.     

LincRNA-p21 alleviates atherosclerosis progression through regulating the miR-221/SIRT1/Pcsk9 axis

Atherosclerosis (AS) is the main aetiology of coronary heart disease, cerebral infarction and peripheral vascular disease in humans. Long-noncoding RNA (LincRNA)-p21 has been reported to participate in the development of AS. Therefore, this study was designed to investigate the mechanism of LincRNA-p21 on suppressing the development of AS. We fed ApoE^−/− mice with a high-fat diet to induce an AS mouse model where the lesion area of AS and the extent of lipid deposition were measured. The binding of LincRNA-p21 and miR-221 or miR-221 and SIRT1 was measured using a dual luciferase reporter gene assay and RIP. Following loss- and gain- function assays, CCK8, EdU, Transwell assay and scratch test were performed to determine the biological processes of human aortic endothelial cells (HAECs). miR-221 was highly expressed while SIRT1 was poorly expressed in AS. LincRNA-p21 acted as a sponge for miR-221. miR-221 targeted and negatively regulated the expression of SIRT1. LincRNA-p21 promoted the deacetylation of Pcsk9 by SIRT1 by competitively binding to miR-221, whereby promoting HAEC proliferation, migration and tube formation. In conclusion, LincRNA-p21 acted as a molecular sponge for miR-221 to promote deacetylation of the promoter region of Pcsk9 by SIRT1, therefore preventing the development of AS.     

Identification,Design and Bio-Evaluation of Novel Hsp90 Inhibitors by Ligand-Based Virtual Screening

Heat shock protein 90 (Hsp90), whose inhibitors have shown promising activity in clinical trials, is an attractive anticancer target. In this work, we first explored the significant pharmacophore features needed for Hsp90 inhibitors by generating a 3D-QSAR pharmacophore model. It was then used to virtually screen the SPECS databases, identifying 17 hits. Compound S1 and S13 exhibited the most potent inhibitory activity against Hsp90, with IC₅₀ value 1.61±0.28 μM and 2.83±0.67 μM, respectively. Binding patterns analysis of the two compounds with Hsp90 revealed reasonable interaction modes. Further evaluation showed that the compounds exhibited good anti-proliferative effects against a series of cancer cell lines with high expression level of Hsp90. Meanwhile, S13 induced cell apoptosis in a dose-dependent manner in different cell lines. Based on the consideration of binding affinities, physicochemical properties and toxicities, 24 derivatives of S13 were designed, leading to the more promising compound S40, which deserves further optimization.