Construction of a genetic linkage map and identification of molecular markers in peach rootstocks for response to peach tree short life syndrome

Peach tree short life (PTSL) is a devastating disease syndrome of peach [Prunus persica (L.) Batsch] caused by multiple factors; the molecular biology of its tolerance/susceptibility is unknown. The difficulty of studying PTSL is that tree survival or death is not obvious until 3 to 5 years after planting when the symptoms of PTSL first appear. Tolerance to PTSL was unknown in Prunus until the rootstock Guardian® ‘BY520-9’ was introduced into commercial orchards in 1994. To study the genetics of the response to PTSL, a controlled F₂ cross was made between Guardian® ‘BY520-9’ selection 3-17-7 (PTSL-tolerant) and Nemaguard (PTSL-susceptible). An F₁ hybrid was then selfed to generate an F₂ population expected to segregate for PTSL response. One hundred fifty-one AFLPs and 21 SSRs, including anchor loci from the Prunus reference genetic map, were used to construct a molecular genetic map based on 100 F₂ seedlings. This map covers a genetic distance of 737 cM with an average marker spacing of 4.7 cM and will be used as a framework to construct a highly saturated molecular genetic map. Of the 140 mapped AFLP markers, 38 were associated with PTSL response, as identified previously by bulked segregant analysis. The distribution of the markers associated with PTSL response on the newly constructed genetic map was compared with the recently published Prunus resistance map. This comparison revealed that some resistance gene analogs and several PTSL-associated AFLP markers were located in the same regions in several Prunus linkage groups: G1, G2, G4, G5, and G6. This peach rootstock map can also be viewed and compared with other Prunus maps in comparative map viewer CMap in the Genome Database for Rosaceae (GDR) at http://www.rosaceae.org     

The Raf-like kinase Raf36 negatively regulates plant resistance against the oomycete pathogen Phytophthora parasitica by targeting MKK2

Oomycetes represent a unique group of plant pathogens that are phylogenetically distant from true fungi and cause significant crop losses and environmental damage. Understanding of the genetic basis of host plant susceptibility facilitates the development of novel disease resistance strategies. In this study, we report the identification of an Arabidopsis thaliana T-DNA mutant with enhanced resistance to Phytophthora parasitica with an insertion in the Raf-like mitogen-activated protein kinase kinase kinase gene Raf36. We generated additional raf36 mutants by CRISPR/Cas9 technology as well as Raf36 complementation and overexpression transformants, with consistent results of infection assays showing that Raf36 mediates Arabidopsis susceptibility to P. parasitica. Using a virus-induced gene silencing assay, we silenced Raf36 homologous genes in Nicotiana benthamiana and demonstrated by infection assays the conserved immune function of Raf36. Mutagenesis analyses indicated that the kinase activity of Raf36 is important for its immune function and interaction with MKK2, a MAPK kinase. By generating and analysing mkk2 mutants and MKK2 complementation and overexpression transformants, we found that MKK2 is a positive immune regulator in the response to P. parasitica infection. Furthermore, infection assay on mkk2 raf36 double mutant plants indicated that MKK2 is required for the raf36-conferred resistance to P. parasitica. Taken together, we identified a Raf-like kinase Raf36 as a novel plant susceptibility factor that functions upstream of MKK2 and directly targets it to negatively regulate plant resistance to P. parasitica.     

Characterization of reduced susceptibility to chlorhexidine among Gram-negative bacteria

Chlorhexidine gluconate (CHG) is one of the most commonly used antiseptic, acting against Gram-negative, Gram-positive bacteria, yeast and fungi. However, over use may lead to reduced susceptibility of different bacteria to CHG. This study aimed to characterize the CHG susceptibility among Gram-negative strains in Israel, to evaluate factors that may affect this susceptibility, and to compare CHG susceptibility between ESBLs bacteria to strains without these enzymes. Pseudomonas aeruginosa, Proteus mirabilis, Klebsiella spp, Escherichia coli, and Acinetobacter baumannii were isolated from clinical samples of 193 patients hospitalized at Padeh–Poriya Medical Center. Phenotypic CHG susceptibility was assessed by determining minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The highest CHG MIC was found among P. mirabilis. The differences between the CHG MIC values among the different strains were statistically significant (p < 0.001). ESBL-positive strains had higher MIC values as compared to ESBL-negative strains (p = 0.030). A significant association was found between CHG susceptibility and sample source (p = 0.015). In conclusion, the information gathered here significantly improves our knowledge on the reduced susceptibility to CHG among Gram-negative bacteria in Israel. Moreover, ESBL-positive bacteria are less susceptible to CHG and finally, bacteria in sputum, wounds, and body fluids are less CHG-susceptible.     

Potential host fruits for Drosophila suzukii: olfactory and oviposition preferences and suitability for development

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), the spotted wing drosophila, is a pest endemic to Southeast Asia that invaded the Americas and Europe in 2008. In contrast to most of its congeners, D. suzukii possesses a serrated ovipositor that allows it to lay eggs in unwounded commercial fruits, resulting in severe revenue losses for the industry. The purpose of this study was to determine the susceptibility of known host fruits, including cherry, strawberry, blueberry, and grape, and potential host fruits, such as banana and apple, to attack by D. suzukii. Based on the responses to volatile cues offered in a six‐choice olfactometer, the preference of female D. suzukii was ranked in the following order: strawberry = cherry > banana = apple = blueberry = grape, but in no‐choice and choice oviposition tests, the preferences were ranked as follows: cherry > strawberry = blueberry > grape = banana > apple. Furthermore, we reconfirmed that D. suzukii mainly targets rotten fruit for feeding and ripe fruit for oviposition, and females preferred fruits with intensive mechanical damage. Based on developmental parameters, apple was the least suitable host. This study has implications for the control of D. suzukii, especially in mixed fruit orchards, by providing a promising avenue for exploiting behaviour‐based control tools and emphasizing the importance of phenology in host fruit susceptibility.     

LncRNA CASC2 inhibits proliferation and migration of adenocarcinoma cells via miR-4735-3p and mTOR

Lung adenocarcinoma is a major form of non–small-cell lung cancer that frequently strikes nonsmokers. The disease is often diagnosed at a late stage and the 5-year survival rate is very low. Although previous studies found many somatic alterations associated with lung adenocarcinoma, the molecular basis of the development and progression of the disease is not well understood. We found that long noncoding RNA (lncRNA) cancer susceptibility candidate 2 (CASC2), a putative tumor suppressor, was downregulated in both patient adenocarcinoma tissues and cultured lung cancer cells. Its tumor suppression function seemed to be dependent on its binding to miR-4735-5p. Changing the levels of CASC2 and miR-4735-3p in the cultured adenocarcinoma cells could affect the malignant phenotypes as well as growth of tumors derived from the cells injected into nude mice. Furthermore, the lncRNA and miR-4735-3p interplay likely the suppressed tumor growth through the downstream mammalian target of rapamycin signaling pathway. The results have revealed molecular details that may be critical for the development of lung adenocarcinoma, opening opportunities for the development of novel, and therapeutic tools.     

Enterotoxin-like activity produced by Campylobacter jejuni and Campylobacter coli isolated from patients and healthy controls in Algeria

Abstract In our earlier studies, hexammine ruthenium (III) chloride (HRC) was found to eliminate the pBR322 plasmid from E. coli HB101 with 100% frequency. However, this plasmid was not eliminated by other known curing agents, such as acridine orange, sodium dodecyl sulphate (SDS), rifampicin or temperature conditions. In our present communication, we report the sensitivity of a variant of plasmid pBR322 to curing agents which were not effective on the parent plasmid.     

Vector competence of selected South African Culicoides species for the Bryanston serotype of equine encephalosis virus

Equine encephalosis virus (EEV) was recognized and described in the Republic of South Africa in 1967 and subsequent serological studies have shown this orbivirus to be both widespread and prevalent in southern Africa. In the present study it was shown that wild-caught Culicoides (Avaritia) imicola Kieffer (Diptera: Ceratopogonidae) can become infected with and permit the replication of the Bryanston serotype of EEV following membrane-feeding on infective blood containing 5.0 log10 plaque-forming-units (PFU)/ml. The mean prevalence of Bryanston virus infection in C. imicola after 10 days extrinsic incubation at 23.5 degrees C was 22.3% (23/103). The mean infectivity of Bryanston virus in the infected C. imicola increased from 1.3 log10 PFU/midge, in insects assayed immediately after feeding on the blood-virus mixture, to 2.6 log10 PFU/midge in insects assayed after incubation. The virus concentration in individual C. imicola infected with the Bryanston serotype of EEV ranged from 0.7 to 3.6 log10 PFU/midge. Bryanston virus titres higher than 2.5 log10 TCID50, found in individual C. imicola, suggest that this species may be able to transmit this virus to susceptible hosts. Prevalence of virus infection in C. imicola was determined by PFU and microtitration assays on both BHK and Vero cells and confirmation of the Bryanston serotype of EEV was determined by plaque inhibition. No virus replication could be demonstrated in 102 C. nivosus tested after the incubation period, suggesting that not all Culicoides species are equally susceptible to Bryanston virus infection. Other Culicoides species that survived the incubation period and that were negative for the presence of Bryanston virus were C. pycnostictus (42), C. leucostictus (7), C. magnus (2), C. bolitinos (1) and C. bedfordi (1).     

Microbiological Characteristics and Susceptibility Patterns of Strains of Rhodotorula Isolated from Clinical Samples

The members of the genus Rhodotorula show a marked ubiquity. In man, they have been isolated from faeces, nails, skin, sputum, digestive tract and adenoids, forming part of the normal human flora, although in recent years cases have been reported of both local and systemic infection by this yeast. There are virtually no studies in the literature on the sensitivity of this genus to the antifungal agents in common clinical use. Therefore, it is considered of interest to study the microbiological characteristics and the susceptibility patterns of Rhodotorula isolated from clinical samples. A total of 35 different strains of Rhodotorula were studied. In vitro susceptibility testing to 5-fluorocytosine, amphotericin B, ketoconazole, fluconazole and itraconazole was performed. All the strains were considered sensitive to 5-fluorocytosine, amphotericin B, ketoconazole and itraconazole and resistant to fluconazole. As a conclusion, we can state that all the antifungal agents tested, except fluconazole, are useful medicaments for the treatment of infections by the Rhodotorula genus. This revised version was published online in June 2006 with corrections to the Cover Date.