DNA primase large subunit is an essential plant gene for geminiviruses, putatively priming viral ss-DNA replication

The family of Geminiviridae consists of more than 500 circular single-stranded (ss) DNA viral species that can infect numerous dicot and monocot plants. Geminiviruses replicate their genome in the nucleus of a plant cell, taking advantage of the host's DNA replication machinery. For converting their DNA into double-stranded DNA, and subsequent replication, these viruses rely on host DNA polymerases. However, the priming of the very first step of this process, i.e. the conversion of incoming circular ssDNA into a dsDNA molecule, has remained elusive for almost 30 years. In this study, sequencing of melon (Cucumis melo) accession K18 carrying the Tomato leaf curl New Delhi virus (ToLCNDV) recessive resistance quantitative trait locus (QTL) in chromosome 11, and analyses of DNA sequence data from 100 melon genomes, showed a conservation of a shared mutation in the DNA Primase Large subunit (PRiL) of all accessions that exhibited resistance upon a challenge with ToLCNDV. Silencing of (native) Nicotiana benthamiana PriL and subsequent challenging with three different geminiviruses showed a severe reduction in titers of all three viruses, altogether emphasizing an important role of PRiL in geminiviral replication. A model is presented explaining the role of PriL during initiation of geminiviral DNA replication, i.e. as a regulatory subunit of primase that generates an RNA primer at the onset of DNA replication in analogy to DNA Primase-mediated initiation of DNA replication in all living organisms.

First Report of Cucurbit chlorotic yellows virus infecting Cucumber Plants in Spain

During the winter 2018, symptoms of leaf chlorotic spots (Figure 1) followed by symptoms of leaf interveinal chlorosis (Figure 2) and severe chlorosis in basal leaves were observed in cucumber cv Laredo (Cucumis sativus) plants in three separated greenhouses, sited in distinct locations in southern Spain. In all cases, Bemisia tabaci populations were observed on infected plants. The symptomology observed was similar to that caused by whitefly transmitted Cucurbit yellow stunting disorder virus (CYSDV, genus Crinivirus, family Closteroviridae), which is usually found infecting cucumber plants in this geographical area (1). Samples from four different cucumber plants of distinct greenhouses were collected and tested for the presence of CYSDV. Total RNA was extracted from the samples using the NucleoSpin RNA Plant kit (Macherey-Nagel, Germany). Molecular detection of CYSDV was performed using the multiplex and degenerate primer RT-PCR method (2), specific to the region of the highly conserved RNA-dependent RNA polymerase (RdRp) gene of criniviruses, which also detects other criniviruses such as Lettuce infectious yellows virus (LIYV) and Beet pseudo-yellows virus (BPYV). Results indicated that the viral species CYSDV, LIYV and BPYV were not detected in the four cucurbit plant samples. In 2004, an emergent crinivirus (Cucurbit chlorotic yellows virus, CCYV), inducing symptoms similar to those caused by CYSDV, was described infecting cucurbits in Japan (3). Recently, CCYV was detected in 2011 in Greece (4) and in 2014 in Egypt (5) and Saudi Arabia (6). Therefore, the four RNA samples were tested for the presence of the CCYV by a RT-PCR method previously described (7). Specific primers were designed to amplify 336 nt of the capsid protein (CP) gene and 680 nt of the RdRp gene, located on CCYV genomic RNA 1 and RNA 2, respectively. In all cases, clear cDNA bands of both expected sizes were detected for each cucumber sample that were then purified and sequenced via Sanger technology. BLAST analysis of those sequences showed 99% identity with the nucleotide sequence of the CP and RpRd genes from the CCYV isolates from Greece (LT992911, LT992910), China (KY400633.1, KX118632) and Taiwan (JF502222). To our knowledge, this is the first report of CCYV infecting cucurbits in Spain. Probably CCYV has been spread throughout the Mediterranean basin, remaining undetected due to the yellowing symptom similarities between CYSDV and CCYV. Detection of the emergent virus CCYV in Spain represents a new threat for the horticultural area of southern Europe.

Oxaloacetate acetylhydrolase gene mutants of Sclerotinia sclerotiorum do not accumulate oxalic acid, but do produce limited lesions on host plants

The oxaloacetate acetylhydrolase (OAH, EC 3.7.1.1)-encoding gene Ss-oah1 was cloned and functionally characterized from Sclerotinia sclerotiorum. Ss-oah1 transcript accumulation mirrored oxalic acid (OA) accumulation with neutral pH induction dependent on the pH-responsive transcriptional regulator Ss-Pac1. Unlike previously characterized ultraviolet (UV)-induced oxalate-deficient mutants ('A' mutants) which retain the capacity to accumulate OA, gene deletion Δss-oah1 mutants did not accumulate OA in culture or during plant infection. This defect in OA accumulation was fully restored on reintroduction of the wild-type (WT) Ss-oah1 gene. The Δss-oah1 mutants were also deficient in compound appressorium and sclerotium development and exhibited a severe radial growth defect on medium buffered at neutral pH. On a variety of plant hosts, the Δss-oah1 mutants established very restricted lesions in which the infectious hyphae gradually lost viability. Cytological comparisons of WT and Δss-oah1 infections revealed low and no OA accumulation, respectively, in subcuticular hyphae. Both WT and mutant hyphae exhibited a transient association with viable host epidermal cells at the infection front. In summary, our experimental data establish a critical requirement for OAH activity in S. sclerotiorum OA biogenesis and pathogenesis, but also suggest that factors independent of OA contribute to the establishment of primary lesions.

Peroxysomal carnitine acetyl transferase influences host colonization capacity in Sclerotinia sclerotiorum

In lower eukaryotes, the glyoxylate cycle allows cells to utilize two-carbon compounds when simple sugars are not available. In filamentous fungi, glyoxylate metabolism is coupled with β-oxidation of fatty acids, and both are localized to ubiquitous eukaryotic organelles called peroxisomes. Acetyl coenzyme A (acetyl-CoA) produced during β-oxidation is transported via the cytosol into mitochondria for further metabolism. A peroxisomal-specific pathway for acetyl-CoA transport requiring peroxisomal carnitine acetyl transferase (CAT) activity has been identified in Magnaporthe grisea peroxisomes. Here, we report that a Sclerotinia sclerotiorum ortholog of the M. grisea peroxisomal CAT-encoding gene Pth2 (herein designated Ss-pth2) is required for virulence-associated host colonization. Null (ss-pth2) mutants, obtained by in vitro transposon mutagenesis, failed to utilize fatty acids, acetate, or glycerol as sole carbon sources for growth. Gene expression analysis of these mutants showed altered levels of transcript accumulation for glyoxylate cycle enzymes. Ss-pth2 disruption also affected sclerotial, apothecial, and appressorial development and morphology, as well as oxalic acid accumulation when cultured with acetate or oleic acid as sole carbon nutrient sources. Although mutants were able to penetrate and initially colonize host tissue, subsequent colonization was impaired. Genetic complementation with the wild-type Ss-pth2 restored wild-type virulence phenotypes. These findings suggest an essential role in S. sclerotiorum for the peroxisomal metabolic pathways for oxalic acid synthesis and host colonization.

A Rapid Resazurin-Based Microtiter Assay to Evaluate QoI Sensitivity for Alternaria alternata Isolates and Their Molecular Characterization

Chemical management of Alternaria brown spot of citrus is based upon the timely application of site-specific fungicides, many of which are vulnerable to the development of fungicide resistance. A rapid microtiter bioassay based on the colorimetric changes of resazurin (RZ) dye was developed to evaluate the sensitivity of Alternaria alternata to quinone outside inhibitor (QoI) fungicides. Four liquid media (complete medium, minimal medium, potato dextrose broth, and yeast peptone dextrose broth), five conidia concentrations (from 10¹ to 10⁵ conidia/ ml), and five RZ concentrations (10, 20, 30, 40, and 50 μM) were evaluated. Complete medium at 10⁵ conidia/ml and 40 μM RZ were identified as optimal for measuring RZ reduction. The effective concentration of two QoI fungicides (azoxystrobin and pyraclostrobin) needed to reduce RZ by 50% (EC₅₀) was calculated and compared with those obtained from conidia germination tests on fungicide-amended media. Concordant EC₅₀ values were observed (R² = 0.923; P < 0.0001) from both methods. Resistant phenotypes were further characterized by the partial sequencing of the cytochrome b gene. Genetic variability associated with the presence or absence of two introns was observed among isolates. The identified resistant isolates had the amino acid substitution G143A, typical of QoI resistance in other fungi.

Evidence for morphological, vegetative, genetic, and mating-type diversity in Sclerotinia homoeocarpa

Morphology, vegetative compatibility groups, and molecular characteristics were compared among 47 isolates of the dollar spot pathogen Sclerotinia homoeocarpa. Isolates were collected from cool- and warm-season turfgrasses in Florida and the northern United States. Mycelial pigment accumulation, substratal stromata formation, and symptom development were used to separate the collection into two distinct morphological types: a common-type (C-type) and a Floridian-type (F-type). Phylogenetic relationships estimated from ITS sequences supported the morphological typing. Identification and characterization of the S. homoeocarpa mating-type locus revealed an idiomorphic organization for both C- and F-types with nearly equal frequencies of each mating types present in both groups. These findings suggest heterothallic control of mating and indicate potential for outcrossing in both groups. Dollar spot disease of turfgrass in Florida is caused by two distinct morphological types of S. homoeocarpa which may be cryptic species. These findings could have implications for disease management.

Further characterization of two sequiviruses infecting lettuce and development of specific RT-PCR primers

Lettuce mottle virus (LeMoV) and dandelion yellow mosaic virus (DaYMV) infect lettuce in South America and Europe, respectively. LeMoV and DaYMV possess isometric particles, occur at low concentrations in plants and have narrow host ranges. Partial genome sequences of both viruses were obtained using purified viral preparations and universal primers for members of the family Sequiviridae. DaYMV and LeMoV sequences were analyzed and showed identity with other members of the family. Universal primers that detect both viruses and specific primers for LeMoV and DaYMV were designed and used in RT-PCR-based diagnostic assays. These results provide the first molecular data on the LeMoV and DaYMV genomes and suggest that LeMoV is a member of the genus Sequivirus, probably distinct from DaYMV.

Effect of moderate red wine intake on cardiac prognosis after recent acute myocardial infarction of subjects with Type 2 diabetes mellitus

BACKGROUND

Oxidative stress and increased inflammation have been reported to be increased in subjects with diabetes and to be involved in the pathogenesis of cardiovascular complications after myocardial infarction (MI). It is well recognized that red wine has antioxidant and anti-inflammatory activities. We examined the effects of moderate red wine intake on echocardiographic parameters of functional cardiac outcome in addition to inflammatory cytokines and nitrotyrosine (oxidative stress marker), in subjects with diabetes after a first uncomplicated MI.

METHODS

One hundred and fifteen subjects with diabetes who had sustained a first non-fatal MI were randomized to receive a moderate daily amount of red wine (intervention group) or not (control group). Echocardiographic parameters of ventricular dys-synchrony, circulating levels of nitrotyrosine, tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), interleukin-18 (IL-18) and C-reactive protein (CRP) were investigated at baseline and 12 months after randomization.

RESULTS

After 1 year of diet intervention, concentrations of nitrotyrosine (P < 0.01), CRP (P < 0.01), TNF-alpha (P < 0.01), IL-6 (P < 0.01) and IL-18 (P < 0.01) were increased in the control group compared with the intervention group. In addition, myocardial performance index (P < 0.02) was higher, and transmitral Doppler flow (P < 0.05), pulmonary venous flow analysis (P < 0.02) and ejection fraction (P < 0.05) were lower in the control group, indicating ventricular dys-synchrony. The concentrations of nitrotyrosine, CRP, TNF-alpha and IL-6 were related to echocardiographic parameters of ventricular dys-synchrony.

CONCLUSIONS

In subjects with diabetes, red wine consumption, taken with meals, significantly reduces oxidative stress and pro-inflammatory cytokines as well as improving cardiac function after MI. Moderate red wine intake with meals may have a beneficial effect in the prevention of cardiovascular complications after MI in subjects with diabetes.

Characterization of Apricot pseudo-chlorotic leaf spot virus, A Novel Trichovirus Isolated from Stone Fruit Trees

ABSTRACT A trichovirus closely related to Apple chlorotic leaf spot virus (ACLSV) was detected in symptomatic apricot and Japanese plum from Italy. The Sus2 isolate of this agent cross-reacted with anti-ACLSV polyclonal reagents but was not detected by broad-specificity anti- ACLSV monoclonal antibodies. It had particles with typical trichovirus morphology but, contrary to ACLSV, was unable to infect Chenopodium quinoa and C. amaranticolor. The sequence of its genome (7,494 nucleotides [nt], missing only approximately 30 to 40 nt of the 5' terminal sequence) and the partial sequence of another isolate were determined. The new virus has a genomic organization similar to that of ACLSV, with three open reading frames coding for a replication-associated protein (RNA-dependent RNA polymerase), a movement protein, and a capsid protein, respectively. However, it had only approximately 65 to 67% nucleotide identity with sequenced isolates of ACLSV. The differences in serology, host range, genome sequence, and phylogenetic reconstructions for all viral proteins support the idea that this agent should be considered a new virus, for which the name Apricot pseudo-chlorotic leaf spot virus (APCLSV) is proposed. APCLSV shows substantial sequence variability and has been recovered from various Prunus sources coming from seven countries, an indication that it is likely to have a wide geographical distribution.

[So-called benign broncho-esophageal fistula]

Broncho-oesophageal fistulae are rare lesions and may be benign or malignant. The articles in medical literature generally concern one case of BEF, and rarely more cases. The term "benign" is debatable, considering the severity of this disease in view of the aetiology and the bronchopulmonary complications. The aetiology in the past was connected to tuberculosis or toxoplasmosis, now to bacterial, viral or fungal infections. The Authors report three acquired cases and one congenital. They confirm the importance of anamnesis, symptomatology and oesophagography for diagnosis and CT scan for detection of pulmonary lesions. The treatment is surgical with resection of fistula and suture of the oesophagus and bronchus, interposing pleura or pericardium or intercostal muscle.