Cytochrome b gene structure and consequences for resistance to Qo inhibitor fungicides in plant pathogens

The cytochrome b (cyt b) gene structure was characterized for different agronomically important plant pathogens, such as Puccinia recondita f sp tritici (Erikss) CO Johnston, P graminis f sp tritici Erikss and Hennings, P striiformis f sp tritici Erikss, P coronata f sp avenae P Syd & Syd, P hordei GH Otth, P recondita f sp secalis Roberge, P sorghi Schwein, P horiana Henn, Uromyces appendiculatus (Pers) Unger, Phakopsora pachyrhizi Syd & P Syd, Hemileia vastatrix Berk & Broome, Alternaria solani Sorauer, A alternata (Fr) Keissl and Plasmopara viticola (Berk & Curt) Berlese & de Toni. The sequenced fragment included the two hot spot regions in which mutations conferring resistance to QoI fungicides may occur. The cyt b gene structure of these pathogens was compared with that of other species from public databases, including the strobilurin-producing fungus Mycena galopoda (Pers) P Kumm, Saccharomyces cerevisiae Meyer ex Hansen, Venturia inaequalis (Cooke) Winter and Mycosphaerella fijiensis Morelet. In all rust species, as well as in A solani, resistance to QoI fungicides caused by the mutation G143A has never been reported. A type I intron was observed directly after the codon for glycine at position 143 in these species. This intron was absent in pathogens such as A alternata, Blumeria graminis (DC) Speer, Pyricularia grisea Sacc, Mycosphaerella graminicola (Fuckel) J Schr?t, M fijiensis, V inaequalis and P viticola, in which resistance to QoI fungicides has occurred and the glycine is replaced by alanine at position 143 in the resistant genotype. The present authors predict that a nucleotide substitution in codon 143 would prevent splicing of the intron, leading to a deficient cytochrome b, which is lethal. As a consequence, the evolution of resistance to QoI fungicides based on G143A is not likely to evolve in pathogens carrying an intron directly after this codon.     

GENETICS. The Human Variome Project

An ambitious plan to collect, curate, and make accessible information on genetic variations affecting human health is beginning to be realized.     

Genome of Geobacter sulfurreducens: metal reduction in subsurface environments

The complete genome sequence of Geobacter sulfurreducens, a delta-proteobacterium, reveals unsuspected capabilities, including evidence of aerobic metabolism, one-carbon and complex carbon metabolism, motility, and chemotactic behavior. These characteristics, coupled with the possession of many two-component sensors and many c-type cytochromes, reveal an ability to create alternative, redundant, electron transport networks and offer insights into the process of metal ion reduction in subsurface environments. As well as playing roles in the global cycling of metals and carbon, this organism clearly has the potential for use in bioremediation of radioactive metals and in the generation of electricity.     

Role of mobile DNA in the evolution of vancomycin-resistant Enterococcus faecalis

The complete genome sequence of Enterococcus faecalis V583, a vancomycin-resistant clinical isolate, revealed that more than a quarter of the genome consists of probable mobile or foreign DNA. One of the predicted mobile elements is a previously unknown vanB vancomycin-resistance conjugative transposon. Three plasmids were identified, including two pheromone-sensing conjugative plasmids, one encoding a previously undescribed pheromone inhibitor. The apparent propensity for the incorporation of mobile elements probably contributed to the rapid acquisition and dissemination of drug resistance in the enterococci.     

Identification of polymers as major components of atmospheric organic aerosols

Results from photooxidation of aromatic compounds in a reaction chamber show that a substantial fraction of the organic aerosol mass is composed of polymers. This polymerization results from reactions of carbonyls and their hydrates. After aging for more than 20 hours, about 50% of the particle mass consists of polymers with a molecular mass up to 1000 daltons. This results in a lower volatility of this secondary organic aerosol and a higher aerosol yield than a model using vapor pressures of individual organic species would predict.     

Determination of some toxic and essential metal ions in medicinal and edible plants from Mali

Plants are used in different ways in Mali, among those as medicine and as food. The monitoring of metals in the plants is of great importance for protecting the public from the hazards of possible toxic effects and also for informing the population about the nutritional value of the plants. The concentrations of some toxic and essential metal ions were surveyed in seven medicinal and edible plants from Mali. Dry ashing of the plant material and subsequent use of atomic absorption spectrophotometry were the analytical methodologies used. Iron, manganese, and zinc were found in high concentrations in some of the plants, i.e., 1.4 and 1.5 mg/g iron in Cuminum cyminum and Bombax costatum, respectively, 243 microg/g manganese in Hibiscus sabdariffa, and 62.8 and 67.1 microg/g zinc in Spilanthes oleracaea and B. costatum, respectively, whereas cobalt and cadmium were not detected in any of the plant material studied. The other ions detected, Cr, Ni, Pb, and Cu, were present in minor amounts, in the ranges of 2.2-17.2 microg/g for Cr, 1.6-8.1 microg/g for Ni, 0.7-5.2 microg/g for Pb, and 2.4-17.1 microg/g for Cu. From a toxicological point of view, none of these plants would be harmful for the user by taking in the plant material in the traditional manner, which is preparing an infusion of the plant using amounts not adding up to those necessary to reach a harmful level of the metal ions detected. The plants B. costatum and C. cyminum could be of interest as sources for iron for humans in the case of too low of a level of hemoglobin.     

Gibberellic acid effects on germination and α-amylase activity of winter wheats

Summary Sensitivity to GA in non-Gai genome winter wheat (Triticum aestivum L.) cultivars was investigated to determine magnitude of variation of the trait, its association with other traits, and effects of geographical location of production. -Amylase enzyme activity was measured before and after treatment with gibberellic acid in 18 cultivars grown at one location and in five cultivars grown at six locations. Dye-labeled starch and agar-starch media procedures were used for the first and second experiments, respectively. -Amylase activity differed significantly among the 18 cultivars after germination in water, germination in GA, and in absolute and relative sensitivity to GA. Cultivars that reacted similarly to GA had some common ancestors in their pedigrees, and -amylase activity and sensitivity to GA were significantly negatively associated with seed weight. -Amylase activity differed between tall and semi-dwarf cultivars in the second experiment, but not in the first experiment. The magnitude of variation in -amylase activity and its relationship to preharvest sprouting susceptibility of the cultivars suggested that the trait can be modified to improve seed dormancy. Significant interactions between cultivar responses to GA and geographical location of grain production suggested that selection should be carried out in several environments.Contribution no. 81-162-j, Department of Agronomy, Kansas State University, Manhattan KS 66506, USA.