Horizontal Transmission of "Candidatus Liberibacter solanacearum" by Bactericera cockerelli (Hemiptera: Triozidae) on Convolvulus and Ipomoea (Solanales: Convolvulaceae)

“Candidatus Liberibacter solanacearum” (Proteobacteria) is an important pathogen of solanaceous crops (Solanales: Solanaceae) in North America and New Zealand, and is the putative causal agent of zebra chip disease of potato. This phloem-limited pathogen is transmitted to potato and other solanaceous plants by the potato psyllid, Bactericera cockerelli (Hemiptera: Triozidae). While some plants in the Convolvulaceae (Solanales) are also known hosts for B. cockerelli, previous efforts to detect Liberibacter in Convolvulaceae have been unsuccessful. Moreover, studies to determine whether Liberibacter can be acquired from these plants by B. cockerelli are lacking. The goal of this study was to determine whether horizontal transmission of Liberibacter occurs among potato psyllids on two species of Convolvulaceae, sweet potato (Ipomoea batatas) and field bindweed (Convolvulus arvensis), which grows abundantly in potato growing regions of the United States. Results indicated that uninfected psyllids acquired Liberibacter from both I. batatas and C. arvensis if infected psyllids were present on plants concurrently with the uninfected psyllids. Uninfected psyllids did not acquire Liberibacter from plants if the infected psyllids were removed from the plants before the uninfected psyllids were allowed access. In contrast with previous reports, PCR did detect the presence of Liberibacter DNA in some plants. However, visible amplicons were faint and did not correspond with acquisition of the pathogen by uninfected psyllids. None of the plants exhibited disease symptoms. Results indicate that horizontal transmission of Liberibacter among potato psyllids can occur on Convolvulaceae, and that the association between Liberibacter and Convolvulaceae merits additional attention.     

Association of common variation in the <Emphasis Type="Italic">PPARA</Emphasis>gene with incident myocardial infarction in individuals with type 2 diabetes: A Go-DARTS study

Background

Common variants of the PPARA gene have been found to associate with ischaemic heart disease in non diabetic men. The L162V variant was found to be protective while the C2528G variant increased risk. L162V has also been associated with altered lipid measures. We therefore sought to determine the effect of PPARA gene variation on susceptibility to myocardial infarction in patients with type 2 diabetes. 1810 subjects with type 2 diabetes from the prospective Go-DARTS study were genotyped for the L162V and C2528G variants in the PPARA gene and the association of the variants with incident non-fatal myocardial infarction was examined. Cox's proportional hazards was used to interrogate time to event from recruitment, and linear regression for analysing association of genotype with quantitative clinical traits.

Results

The V162 allele was associated with decreased risk of non-fatal myocardial infarction (HR = 0.31, 95%CI 0.10–0.93 p = 0.037) whereas the C2528 allele was associated with increased risk (HR = 2.77 95%CI 1.34–5.75 p = 0.006). Similarly V162 was associated with a later mean age of diagnosis with type 2 diabetes and C2582 an earlier age of diagnosis. C2528 was also associated with increased total cholesterol and LDL cholesterol, which did not account for the observed increased risk. Haplotype analysis demonstrated that when both rare variants occurred on the same haplotype the effect of each was abrogated.

Conclusion

Genetic variation at the PPARA locus is important in determining cardiovascular risk in both male and female patients with diabetes. This genotype associated risk appears to be independent of the effect of these genotypes on lipid profiles and age of diagnosis with diabetes.

     

Specific residues in plasmatocyte-spreading peptide are required for receptor binding and functional antagonism of insect immune cells

Plasmatocyte-spreading peptide (PSP) is a 23-amino acid cytokine that activates a class of insect immune cells called plasmatocytes. PSP consists of two regions: an unstructured N terminus (1-6) and a highly structured core (7-23). Prior studies identified specific residues in both the structured and unstructured regions required for biological activity. Most important for function were Arg13, Phe3, Cys7, Cys19, and the N-terminal amine of Glu1. Here we have built on these results by conducting cell binding and functional antagonism studies. Alanine replacement of Met12 (M12A) resulted in a peptide with biological activity indistinguishable from PSP. Competitive binding experiments using unlabeled and 125I-M12A generated an IC50 of 0.71 nm and indicated that unlabeled M12A, at concentrations > or =100 nm, completely blocked binding of label to hemocytes. We then tested the ability of other peptide mutants to displace 125I-M12A at a concentration of 100 nm. In the structured core, we found that Cys7 and Cys19 were essential for cell binding and functional antagonism, but these effects were likely because of the importance of these residues for maintaining the tertiary structure of PSP. Arg13, in contrast, was also essential for binding and activity but is not required for maintenance of structure. In the unstructured N-terminal region, deletion of the phenyl group from Phe3 yielded a peptide that reduced binding of 125I-M12A 326-fold. This and all other mutants of Phe3 we bioassayed were unable to antagonize PSP. Deletion of Glu1 in contrast had almost no effect on binding and was a strong functional antagonist. Experiments using a photoaffinity analog indicated that PSP binds to a single 190-kDa protein.     

Approaches to radioiodination of insect neuropeptides

High quality radioiodinated neuropeptides are essential to radioimmunoassays (RIA) and receptor binding assays. Approaches of direct and indirect labeling of neuropeptides with 125Iodine (125I) are compared. An HPLC equipped with an in-line gamma detector and UV absorbance detector was used to evaluate selected labeling methods and products. Treatment of [Y(1)]-adipokinetic hormone-I ([Y(1)]-AKH-I) with chloramine-T caused oxidative damage, whereas enzymatic labeling with lactoperoxidase in the presence of H(2)O(2) produced a good yield of intact, apparently monoiodinated peptide. Labeling of the FMRFamide-related peptide (YGGFMRFa), with chloramine-T apparently formed the methionine sulfoxide, which subsequently could be reduced with dithiothreitol. Products of high specific activity typically are achievable.