Semi‐field evaluation of a granulovirus and Bacillus thuringiensis ssp. kurstaki for season‐long control of the potato tuber moth,Phthorimaea operculella

There are few insecticidal options for potato tuber moth (PTM), Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae), control late in the growing season. We evaluated the PTM granulovirus (PoGV) and Bacillus thuringiensis Berliner ssp. kurstaki (Btk) for season‐long control of PTM on potato foliage in 2006 and 2007. Compared to untreated controls, 10 weekly applications of PoGV (10¹³ occlusion bodies/ha) reduced PTM populations in replicated 1‐m³ field cages by 86–96% on pre‐harvest foliage and 90–97% on tubers added to cages shortly before harvest. Infection rates of 82–95% of L4 larvae by PoGV were noted within individual larval cohorts. Equivalently timed Btk treatments (1.12 kg product/ha) were significantly less effective at population suppression, with a 36–76% reduction in larvae recovered from tubers added to cages. A PoGV/Btk alternation was significantly more effective than Btk alone and as effective as PoGV in 2007, but not in 2006. There was some evidence that reduced rate PoGV treatments (10% rate or 50% application frequency) were less effective than the standard program. There were no treatment effects on percentage of tubers growing in the ground that were infested at harvest, which remained comparatively low at ≤8.1%. Bioassays were conducted to evaluate the residual activities of foliar deposits. Early‐season applications were highly effective for the first 24 h (≥93% mortality) with a steady decline in activity over 10 days. A second application, applied later in the season, showed similar patterns, although in this case Btk was less persistent than PoGV, whereas both agents provided significant larval mortality compared with controls over 14 days. Both PoGV and Btk provide alternatives to manage field infestations of PTM prior to harvest, thus reducing the risk of tuber infestations in storage.     

Cell ultrastructural changes correlate with circadian rhythms in Pyrocystis lunula (Pyrrophyta)

Pyrocystis lunula (Schutt) Schutt has long been a model cell system in the study of circadian rhythms of bioluminescence and photosynthesis. Despite this, relatively little is known about the cell's ultrastructure. Here we report the complete serial reconstruction of P. lunula cells during both day and night phases (the first four dimensional study of any dinoflagellate). This permitted us to track both positional and ultrastructural changes in plastids and scintillons (the organelles responsible for bioluminescence). In daytime cells, plastids extended radially from the cell center with thylakoid membranes in stacks of two. Daytime scintillons clustered in a central region of the cell surrounded by the C-shaped nucleus. During the night, plastids were closely associated in the cell center with their thylakoids stacked in a grana-like arrangement. Nighttime scintillons were spread into the cell periphery. The daily migration of plastids and scintillons may depend on these organelles' interactions with the cells' cytoskeletal framework and appears to be under control of the circadian clock.     

5-halogenated pyrimidine lesions within a CpG sequence context mimic 5-methylcytosine by enhancing the binding of the methyl-CpG-binding domain of methyl-CpG-binding protein 2 (MeCP2)

Perturbations in cytosine methylation signals are observed in the majority of human tumors; however, it is as yet unknown how methylation patterns become altered. Epigenetic changes can result in the activation of transforming genes as well as in the silencing of tumor suppressor genes. We report that methyl-CpG-binding proteins (MBPs), specific for methyl-CpG dinucleotides, bind with high affinity to halogenated pyrimidine lesions, previously shown to result from peroxidase-mediated inflammatory processes. Emerging data suggest that the initial binding of MBPs to methyl-CpG sequences may be a seeding event that recruits chromatin-modifying enzymes and DNA methyltransferase, initiating a cascade of events that result in gene silencing. MBD4, a protein with both methyl-binding and glycosylase activity demonstrated repair activity against a series of 5-substituted pyrimidines, with the greatest efficiency against 5-chlorouracil, but undetectable activity against 5-chlorocytosine. The data presented here suggest that halogenated pyrimidine damage products can potentially accumulate and mimic endogenous methylation signals.     

On the discriminability of hROIs, human visually selected regions-of-interest

Many studies have tried to answer an important question: is it possible to predict human visually selected regions-of-interest (hROIs)? hROIs are defined as the loci of eye fixations and they can be analyzed by their spatial distribution over the visual stimulus and their temporal ordering. We used a simplified set of geometrical spatial kernels and linear filter models as bottom-up conspicuity operators that produce algorithmically selected regions-of-interest, aROIs. As a direct approach we measured the ability of these aROIs to predict human scanpaths. The level of prediction is measured by two similarity indices: S _p for spatial similarity and S _s for temporal ordering similarity. At the same time we assessed the discriminability of the hROI loci, in terms of conspicuity, with respect to non-selected (not of interest) regions of an image. We prove that this discrimination is possible and further correlates with the positional similarity index S _p . Other human scanpath experimental conditions are presented in parsing diagrams and discussed. A general top–down/bottom–up scanpath model is finally formulated.