Inheritance of virulence in the root rot pathogen Phytophthora sojae

The oomycete Phytophthora sojae causes stem and root rot of soybean plants. The interaction of pathogen avirulence (Avr) and host resistance (R)-genes determine the disease outcome. The Avr3a mRNA transcript level is variable among P. sojae strains and determines virulence towards the R-gene Rps3a. To study the inheritance of virulence, genetic crosses and self-fertilizations were performed. A cross between P. sojae strains ACR10 and P7076 causes transgenerational gene silencing of Avr3a allele, and this effect is meiotically stable up to the F5 generation. However, test-crosses of F1 (Avr3aACR10/Avr3aP7076) with strain P6497 result in expression of Avr3a in all progeny and release of silencing of the Avr3aP7076 allele. Progeny from P6497 X ACR10 crosses showed unusual inheritance for Avr3a expression. Overall, we conclude that Avr3a gene silencing is strain specific and could rely on epistatic factors. This study will lead to a better understanding of infection and virulence mechanisms that will help to better manage and safeguard soybean production

Outbreak of pandemic influenza A/H1N1 2009 in Nepal

<p>Abstract</p> <p>Background</p> <p>The 2009 flu pandemic is a global outbreak of a new strain of H1N1 influenza virus. Pandemic influenza A (H1N1) 2009 has posed a serious public health challenge world-wide. Nepal has started Laboratory diagnosis of Pandemic influenza A/H1N1 from mid June 2009 though active screening of febrile travellers with respiratory symptoms was started from April 27, 2009.</p> <p>Results</p> <p>Out of 609 collected samples, 302 (49.6%) were Universal Influenza A positive. Among the influenza A positive samples, 172(28.3%) were positive for Pandemic influenza A/H1N1 and 130 (21.3%) were Seasonal influenza A. Most of the pandemic cases (53%) were found among young people with ≤ 20 years. Case Fatality Ratio for Pandemic influenza A/H1N1 in Nepal was 1.74%. Upon Molecular characterization, all the isolated pandemic influenza A/H1N1 2009 virus found in Nepal were antigenically and genetically related to the novel influenza A/CALIFORNIA/07/2009-LIKE (H1N1)v type.</p> <p>Conclusion</p> <p>The Pandemic 2009 influenza virus found in Nepal were antigenically and genetically related to the novel A/CALIFORNIA/07/2009-LIKE (H1N1)v type.</p

Epigenetic control of effectors in plant pathogens

Plant pathogens display impressive versatility in adapting to host immune systems. Pathogen effector proteins facilitate disease but can become avirulence (Avr) factors when the host acquires discrete recognition capabilities that trigger immunity. The mechanisms that lead to changes to pathogen Avr factors that enable escape from host immunity are diverse, and include epigenetic switches that allow for reuse or recycling of effectors. This perspective outlines possibilities of how epigenetic control of Avr effector gene expression may have arisen and persisted in plant pathogens, and how it presents special problems for diagnosis and detection of specific pathogen strains or pathotypes

Strain Specific Factors Control Effector Gene Silencing in Phytophthora sojae.

The Phytophthora sojae avirulence gene Avr3a encodes an effector that is capable of triggering immunity on soybean plants carrying the resistance gene Rps3a. P. sojae strains that express Avr3a are avirulent to Rps3a plants, while strains that do not are virulent. To study the inheritance of Avr3a expression and virulence towards Rps3a, genetic crosses and self-fertilizations were performed. A cross between P. sojae strains ACR10 X P7076 causes transgenerational gene silencing of Avr3a allele, and this effect is meiotically stable up to the F5 generation. However, test-crosses of F1 progeny (ACR10 X P7076) with strain P6497 result in the release of silencing of Avr3a. Expression of Avr3a in the progeny is variable and correlates with the phenotypic penetrance of the avirulence trait. The F1 progeny from a direct cross of P6497 X ACR10 segregate for inheritance for Avr3a expression, a result that could not be explained by parental imprinting or heterozygosity. Analysis of small RNA arising from the Avr3a gene sequence in the parental strains and hybrid progeny suggests that the presence of small RNA is necessary but not sufficient for gene silencing. Overall, we conclude that inheritance of the Avr3a gene silenced phenotype relies on factors that are variable among P. sojae strains

Etiology of Diarrhoea with Reference to Multiple Drug Resistant Enteric Bacterial Pathogens

A total of 340 stool samples were processed and studied from both sexes including all ages of patients. Association of enteropathogens between male and female was not statistically significant. Incidence of diarrhoea (28.23%) as well as prevalence of enteropathogens (34.31%) was found highest in the age group (20-30) years. The highest prevalence of enteropathogens (44.87%) was found in August. Of the total isolated enteropathogens, Vibrio cholerae O1 was observed in 51.96 % followed by Shigella (18.6%) and Salmonella (8.82%) and parasites were also detected from 20.58 % samples. All isolated V. cholerae O1 were El Tor, Inaba. Among Shigella, majority of isolates were S. flexneri. Among Salmonella, S. typhi, S. typhimurium and Salmonella spp. (polyvalent A-S positive) were identified. Entamoeba histolytica, Girdia lamblia, Ascaris lumbricoides and Trichuris trichiura were isolated among parasites. All isolated (100%) V. cholerae O1 were resistant to nalidixic acid and cotrimoxazole, whereas 68%; 63%; 53%; 37 % and 11% Shigella were resistant to nalidixic acid, ampicillin, cotrimoxazol, mecillinam and ciprofloxacin respectively. Similarly, 55.5%; 44.4 % and 11.1 % Salmonella were resistant to nalidixic acid; ampicillin and cotrimoxazole respectively. All V. cholerae strains, 10 strains of Shigella and 2 strains of Salmonella were found multi drug resistant (MDR). The clinical history of the positive cases revealed that abdominal pain, fever, vomiting, dehydration and nausea were the symptoms of enteric infection. Key words: antibiotics, isolates, enteropathogen, Inab

Parentage, virulence outcomes, and <i>Avr3a</i> transcript detection in F₁ hybrids of <i>P</i>. <i>sojae</i> P6497 X ACR10

<p>Parentage, virulence outcomes, and <i>Avr3a</i> transcript detection in F₁ hybrids of <i>P</i>. <i>sojae</i> P6497 X ACR10</p

Virulence outcomes and <i>Avr3a</i> transcript detection in F₄ and F₅ progeny from <i>P</i>. <i>sojae</i> cross ACR10 X P7076.

<p>Virulence outcomes and <i>Avr3a</i> transcript detection in F₄ and F₅ progeny from <i>P</i>. <i>sojae</i> cross ACR10 X P7076.</p

Segregation analysis for F₂ populations developed from virulent and avirulent F₁ hybrids of P6497 X ACR10.

<p>Segregation analysis for F₂ populations developed from virulent and avirulent F₁ hybrids of P6497 X ACR10.</p

Analysis for <i>Avr3a</i> transcripts in parental <i>P</i>. <i>sojae</i> strains and progeny of cross P6497 X ACR10.

<p>The DNA products from RT-PCR analysis are shown after electrophoresis in agarose gels and visualization with fluorescent dye. The cDNA was synthesized using total RNA isolated from the mycelia of <i>P</i>. <i>sojae</i>. RT-PCR was carried out using gene specific primers for the <i>P</i>. <i>sojae Avr3a</i> and <i>Actin</i> genes. <i>P</i>. <i>sojae</i> strains are indicated above each lane; M, marker lane.</p