Resistance to Fluopicolide and Propamocarb and Baseline Sensitivity to Ethaboxam Among Isolates of Pseudoperonospora cubensis From the Eastern United States.

Chemical control is currently the most effective method for controlling cucurbit downy mildew (CDM) caused by Pseudoperonospora cubensis. Most commercial cucurbit cultivars, with the exception of a few new cucumber cultivars, lack adequate disease resistance. Fluopicolide and propamocarb were among the most effective fungicides against CDM in the United States between 2006 and 2009. Since then, reduced efficacy of these two fungicides under field conditions was reported starting around 2013 but occurrence of resistance to fluopicolide and propamocarb in field isolates of P. cubensis had not been established. Thirty-one isolates collected from cucurbits in the eastern United States were tested for their sensitivity to fluopicolide and propamocarb using a leaf disc assay. This same set of isolates and four additional isolates (i.e., 35 isolates) were also used to establish the baseline sensitivity of P. cubensis to ethaboxam, an ethylamino-thiazole-carboxamide fungicide, which was recently granted registration to control CDM in the United States. About 65% of the isolates tested were resistant to fluopicolide with at least one resistant isolate being present in samples collected from 12 of the 13 states in the eastern United States. About 74% of the isolates tested were sensitive to propamocarb with at least one resistant isolate being among samples collected from 8 of the 12 states in the study. The frequency of resistance to fluopicolide and propamocarb was high among isolates collected from cucumber, while the frequency was low among isolates collected from other cucurbit host types. All isolates tested were found to be sensitive to ethaboxam and EC50 values ranged from 0.18 to 3.08 mg a.i./liter with a median of 1.55 mg a.i./liter. The ratio of EC50 values for the least sensitive and the most sensitive isolate was 17.1, indicating that P. cubensis isolates were highly sensitive to ethaboxam. The most sensitive isolates to ethaboxam were collected from New York, North Carolina, and Ohio, while the least sensitive isolates were collected from Georgia, Michigan, and New Jersey. These results show that ethaboxam could be a viable addition to fungicide programs used to control CDM in the United States.

Active-site variants of Streptomyces griseus protease B with peptide-ligation activity.

BACKGROUND: Peptide-ligating technologies facilitate a range of manipulations for the study of protein structure and function that are not possible using conventional genetic or mutagenic methods. To different extents, the currently available enzymatic and nonenzymatic methodologies are synthetically demanding, sequence-dependent and/or sensitive to denaturants. No single coupling method is universally applicable. Accordingly, new strategies for peptide ligation are sought. RESULTS: Site-specific variants (Ser195-->Gly, S195G, and Ser195-->Ala, S195A) of Streptomyces griseus protease B (SGPB) were generated that efficiently catalyze peptide ligation (i.e., aminolysis of ester-, thioester- and para-nitroanilide-activated peptides). The variants also showed reduced hydrolytic activity relative to the wild-type enzyme. The ratio of aminolysis to hydrolysis was greater for the S195A variant, which was also capable of catalyzing ligation in concentrations of urea as high as 2 M. CONCLUSIONS: Mutagenic substitution of the active-site serine residue of SGPB by either glycine or alanine has created a unique class of peptide-ligating catalysts that are useful for coupling relatively stable ester- and para-nitroanilide-activated substrates. Ligation proceeds through an acyl-enzyme intermediate involving His57. Serine to alanine mutations may provide a general strategy for converting proteases with chymotrypsin-like protein folds into peptide-coupling enzymes.

Adolescent use of alternative and complementary therapies. A framework for research.

Increasing numbers of U.S. adolescents are using alternative and complementary therapies, seemingly mirroring the trend among adults. Patterns of use among adolescents may be different from those of adults, however, due to the unique biological, psychological, and social factors affecting this population. Although there is a growing body of literature on utilization and efficacy of alternative and complementary therapies, few studies have included or focused on adolescents. Such research is needed. Social learning theory provides an appropriate theoretical framework to address the complex web of factors underlying health-care-seeking behavior of adolescents, allowing for consideration of the critical factor of individual expectations in their health care choices. Research on adolescents' utilization of alternative and complementary therapies is important for providers and policy makers concerned with the present and future health of youth.