A mitogen-activated protein kinase gene (MGV1) in Fusarium graminearum is required for female fertility,heterokaryon formation,and plant infection

Fusarium graminearum is an important pathogen of small grains and maize in many areas of the world. Infected grains are often contaminated with mycotoxins harmful to humans and animals. During the past decade, F. graminearum has caused several severe epidemics of head scab in wheat and barley. In order to understand molecular mechanisms regulating fungal development and pathogenicity in this pathogen, we isolated and characterized a MAP kinase gene, MGV1, which is highly homologous to the MPS1 gene in Magnaporthe grisea. The MGV1 gene was dispensable for conidiation in F. graminearum but essential for female fertility during sexual reproduction. Vegetative growth of mgv1 deletion mutants was normal in liquid media but reduced on solid media. Mycelia of the mgv1 mutants had weak cell walls and were hypersensitive to cell wall degrading enzymes. Interestingly, the mgv1 mutants were self-incompatible when tested for heterokaryon formation, and their virulence was substantially reduced. The ability of the mutants to accumulate trichothecene mycotoxins on inoculated wheat was also greatly reduced. Our data suggest that MGV1 in F. graminearum is involved in multiple developmental processes related to sexual reproduction, plant infection, and cell wall integrity.     

Calorie restriction reduces biomarkers of cellular senescence in humans

Calorie restriction (CR) with adequate nutrient intake is a potential geroprotective intervention. To advance this concept in humans, we tested the hypothesis that moderate CR in healthy young-to-middle-aged individuals would reduce circulating biomarkers of cellular senescence, a fundamental mechanism of aging and aging-related conditions. Using plasma specimens from the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE™) phase 2 study, we found that CR significantly reduced the concentrations of several senescence biomarkers at 12 and 24 months compared to an ad libitum diet. Using machine learning, changes in biomarker concentrations emerged as important predictors of the change in HOMA-IR and insulin sensitivity index at 12 and 24 months, and the change in resting metabolic rate residual at 12 months. Finally, using adipose tissue RNA-sequencing data from a subset of participants, we observed a significant reduction in a senescence-focused gene set in response to CR at both 12 and 24 months compared to baseline. Our results advance the understanding of the effects of CR in humans and further support a link between cellular senescence and metabolic health.     

Multilocus genotyping and molecular phylogenetics resolve a novel head blight pathogen within the Fusarium graminearum species complex from Ethiopia

A survey of Fusarium head blight (FHB)-contaminated wheat in Ethiopia recovered 31 isolates resembling members of the Fusarium graminearum species complex. Results of a multilocus genotyping (MLGT) assay for FHB species and trichothecene chemotype determination suggested that 22 of these isolates might represent a new species within the Fg complex. Phylogenetic analyses of multilocus DNA sequence data resolved the 22 Ethiopian isolates as a novel, phylogenetically distinct species. The new species also appears to be novel in that MLGT probe data and sequence analysis of both ends of the TRI-cluster identified 15ADON and NIV recombination blocks, documenting inter-chemotype recombination involving the chemotype-determining genes near the ends of the TRI-cluster. Results of pathogenicity experiments and analyses of trichothecene mycotoxins demonstrated that this novel Fg complex species could induce FHB on wheat and elaborate 15ADON in planta. Herein the FHB pathogen from Ethiopia is formally described as a novel species.     

Conidial germination in the filamentous fungus Fusarium graminearum

The ascomycetous fungus Fusarium graminearum is an important plant pathogen causing Fusarium head blight disease of wheat and barley. To understand early developmental stages of this organism, we followed the germination of macroconidia microscopically to understand the timing of key events. These events, recorded after suspension of spores in liquid germination medium, included spore swelling at 2h, germination tube emergence and elongation from conidia at 8h and hyphal branching at 24h. To understand changes in gene expression during these developmental changes, RNA was isolated from spores and used to interrogate the F. graminearum Affymetrix GeneChip. RNAs corresponding to 5813 genes were detected in fresh spores and 5146, 5249 and 5993, respectively, in spores incubated in germination medium after 2, 8 or 24h (P<0.001). Gene expression data were used to predict the cellular and physiological state of each developmental stage for known processes. Predictions were confirmed microscopically for several previously unreported developmental events such as manifestation of peroxisomes in fresh spores and nuclear division resulting in binuclear cells within macroconidia prior to spore germination. Knowledge of stage-specific gene expression and changes in gene expression levels between developmental stages are an important first step to understanding the molecular mechanisms responsible for spore germination and development.     

Changes in Weight,Waist Circumference and Compensatory Responses with Different Doses of Exercise among Sedentary,Overweight Postmenopausal Women

Background

It has been suggested that exercise training results in compensatory mechanisms that attenuate weight loss. However, this has only been examined with large doses of exercise. The goal of this analysis was to examine actual weight loss compared to predicted weight loss (compensation) across different doses of exercise in a controlled trial of sedentary, overweight or obese postmenopausal women (n = 411).

Methodology/Principal Findings

Participants were randomized to a non-exercise control (n = 94) or 1 of 3 exercise groups; exercise energy expenditure of 4 (n = 139), 8 (n = 85), or 12 (n = 93) kcal/kg/week (KKW). Training intensity was set at the heart rate associated with 50% of each woman''s peak VO₂ and the intervention period was 6 months. All exercise was supervised. The main outcomes were actual weight loss, predicted weight loss (exercise energy expenditure/ 7700 kcal per kg), compensation (actual minus predicted weight loss) and waist circumference. The study sample had a mean (SD) age 57.2 (6.3) years, BMI of 31.7 (3.8) kg/m², and was 63.5% Caucasian. The adherence to the intervention was >99% in all exercise groups. The mean (95% CI) weight loss in the 4, 8 and 12 KKW groups was −1.4 (−2.0, −0.8), −2.1 (−2.9, −1.4) and −1.5 (−2.2, −0.8) kg, respectively. In the 4 and 8 KKW groups the actual weight loss closely matched the predicted weight loss of −1.0 and −2.0 kg, respectively, resulting in no significant compensation. In the 12 KKW group the actual weight loss was less than the predicted weight loss (−2.7 kg) resulting in 1.2 (0.5, 1.9) kg of compensation (P<0.05 compared to 4 and 8 KKW groups). All exercise groups had a significant reduction in waist circumference which was independent of changes in weight.

Conclusion

In this study of previously sedentary, overweight or obese, postmenopausal women we observed no difference in the actual and predicted weight loss with 4 and 8 KKW of exercise (72 and 136 minutes respectively), while the 12 KKW (194 minutes) produced only about half of the predicted weight loss. However, all exercise groups had a significant reduction in waist circumference which was independent of changes in weight.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT 00011193","term_id":"NCT00011193"}}NCT 00011193     

Transducin Beta-Like Gene FTL1 Is Essential for Pathogenesis in Fusarium graminearum

Fusarium head blight caused by Fusarium graminearum is an important disease of wheat and barley. In a previous study, we identified several mutants with reduced virulence by insertional mutagenesis. A transducin beta-like gene named FTL1 was disrupted in one of these nonpathogenic mutants. FTL1 is homologous to Saccharomyces cerevisiae SIF2, which is a component of the Set3 complex involved in late stages of ascospore formation. The Δftl1 mutant was significantly reduced in conidiation and failed to cause typical disease symptoms. It failed to colonize the vascular tissues of rachis or cause necrosis on the rachis of inoculated wheat heads. The Δftl1 mutant also was defective in spreading from infected anthers to ovaries and more sensitive than the wild type to plant defensins MsDef1 and osmotin. However, the activation of two mitogen-activated protein kinases, Mgv1 and Gpmk1, production of deoxynivalenol, and expression of genes known to be important for plant infection in F. graminearum were not affected, indicating that the defect of the Δftl1 mutant in plant infection is unrelated to known virulence factors in this pathogen and may involve novel mechanisms. The Δftl1 deletion mutant was significantly reduced in histone deacetylation, and many members of the yeast Set3 complex are conserved in F. graminearum. FTL1 appears to be a component of this well-conserved protein complex that plays a critical role in the penetration and colonization of wheat tissues.The filamentous ascomycete Fusarium graminearum (teleomorph Gibberella zeae) is the main causal agent of Fusarium head blight (FHB), or scab, which is an important disease on wheat and barley throughout the world (18). It also causes stalk and ear rots of maize and infects other small grains. In addition to causing yield losses, this pathogen often contaminates infested grains with trichothecene and estrogenic mycotoxins, such as deoxynivalenol (DON) and zearalenone. Unfortunately, complete resistance to F. graminearum is lacking in wheat, and fungicide application is not cost-effective for FHB control in wheat and barley.F. graminearum overwinters in infected plant debris and produces ascospores in the spring. Ascospores are forcibly discharged from mature perithecia (52) and function as the primary inoculum for FHB. The multicellular conidia or macroconidia are important for spreading the disease in the field and colonizing plant vegetative tissues. Wheat spikes are most susceptible to FHB at anthesis (34a). Although F. graminearum can colonize glumes, anthers are the main site of primary infection on flowering wheat heads (3, 38). Earlier studies indicated that wheat anther extracts stimulate F. graminearum virulence on wheat. Choline and glycine betaine were identified as two major components in anthers that stimulate fungal growth and predispose wheat to F. graminearum infection (50, 51). Under conducive conditions, the fungus can spread from the infected floret along the rachis and cause severe damage. The production of DON, the first virulence factor identified in F. graminearum (11, 42), is not necessary for the initial infection but is important for the spread of FHB on infected wheat heads (2).In the past few years, genetic and genomic studies of F. graminearum have advanced significantly. The genome of F. graminearum has been sequenced (10) and a whole-genome microarray of this haploid homothallic fungus is commercially available (21). A number of pathogenicity or virulence factors have been identified by insertional mutagenesis or targeted gene deletion approaches. Two mitogen-activated protein (MAP) kinase genes, MGV1 and GPMK1, are essential for pathogenicity in F. graminearum (23, 24). Genes that are important for full virulence in F. graminearum on wheat include FGL1 (54), GzCPS1 (31), FBP1 (22), FSR1 (48), SID1 (19), NPS6 (37), RAS2 (5), GzGPA2 and GzGPB1 (56), and HMR1 (47). These virulence-associated genes encode proteins with various biochemical activities, such as lipase, nonribosomal peptide synthase, Ras protein, and 3-hydroxy 3-methylglutaryl coenzyme A reductase. Several genes involved in the primary metabolism, such as the CBL1, RSY1, GzHIS7, ADE5, and ARG2 genes (29, 44, 46) that are required for methionine, histidine, and arginine syntheses, also have been implicated in plant infection in F. graminearum. Overall, molecular mechanisms underlying F. graminearum pathogenesis appear to be complex and remain to be fully understood.In a previous study, we identified 11 restriction enzyme-mediated integration (REMI) mutants that are defective in plant infection (46). In one of these mutants, the transforming vector was inserted in a predicted gene named FTL1 (for Fusarium transducin beta-like gene 1). FTL1 is homologous to the mammalian TBL1 or TBLR1 genes (40, 55) and the Saccharomyces cerevisiae SIF2 gene (8). The products of these genes are components of protein complexes involving histone deacetylases (HDACs). In mammalian cells, TBL1 and TBLR1 are parts of the N-CoR/SMRT/HDAC complexes (40). In yeast, SIF2 is a part of the Set3 complex regulating ascospore formation. In F. graminearum, the Δftl1 gene replacement mutant was significantly reduced in conidiation and failed to cause typical head blight symptoms on flowering wheat heads. It failed to colonize vascular tissues or cause necrosis on the rachis of inoculated wheat heads. The Δftl1 mutant also was defective in spreading from infected anthers to ovaries and was more sensitive than the wild type to plant defensins MsDef1 and osmotin. Although it was normal in the production of deoxynivalenol and the expression of known virulence factors, the Δftl1 mutant was significantly reduced in HDAC activities. FTL1 appears to be a component of this well-conserved HDAC complex that plays a critical role in the penetration and colonization of wheat tissues.