The importance of cryptic species and subspecific populations in classic biological control of weeds: a North American perspective

Classical biological control of weeds depends on finding agents that are highly host-specific. This requires not only correctly understanding the identity of the target plant, sometimes to subspecific levels, in order to find suitable agents, but also identifying agents that are sufficiently specific to be safe and effective. Behavioral experiments and molecular genetic tools have revealed that some arthropod species previously thought to be polyphagous really consist of multiple cryptic species, host races or biotypes, some of which are more host-specific than others. Whereas true species are reproductively isolated, individuals from subspecific populations may potentially interbreed with those of other populations if they should encounter them. Furthermore, biotypes may consist of individuals sharing a genotype that is not fixed within a monophyletic group, and thus may not be evolutionarily stable. This raises the question of how such populations should be classified, and how to confirm the identity of live arthropods before releasing them as classical biological control agents. The existence of host races or cryptic species may greatly increase the number of prospective biological control agents available. However, it may also create new challenges for governmental regulation. These issues are discussed using pertinent examples, mainly from North America.     

Polypropionate lactones of deoxysugars glycosides from slime mold Lycogala epidendrum

Two novel polypropionate lactone glycosides (1 and 2, i.e. lycogalinosides A and B) were isolated from the slime mold Lycogala epidendrum. Their structures, including the absolute configurations of the hydroxyl and methyls groups, were determined by means of extensive spectroscopic data such as mass, IR, UV, and 1D and 2D NMR spectra and chemical degradation followed by spectroscopic and chromatographic analysis. Compounds 1 and 2 are unique in structure containing a 2-deoxy-alpha-L-fucopyranosyl-(1-4)-6-deoxy-beta-D-gulopyranosyl unit and a beta-D-olivopyranosyl-(1-4)-beta-D-fucopyranosyl unit, respectively, and showed growth inhibitory activities against Gram-positive bacteria.     

Changes in cortisol binding to soluble receptor proteins in rat liver and thymus during development and ageing.

Changes in labeled cortisol binding to soluble cytoplasmic proteins of rat liver and thymus during development and ageing of animals have been observed.The relationship of age and cortisol binding to a fraction of soluble liver proteins precipitated at 50% saturation with ammonium sulfate displayed two maxima: The first one on the seventh day of postnatal life and the second one at 2.5 months of age. Binding of hormone to macromolecules of the same fraction prepared from older animals was less efficient. Almost the same picture has been obtained when total bound activity to macromolecular cytosol fraction was expressed per milligram of dry weight of liver.Binding of labeled cortisol to total cytosol macromolecules of liver and thymus was most efficient in 3-month-old animals and decreased after that, which is of interest in view of totally opposite effects of glucocorticoids upon various biosynthetic processes of these organs.     

Passive Avoidance Learning Results in Region-Specific Changes in Concentration of and Incorporation into Colchicine-Binding Proteins in the Chick Forebrain

Abstract: Incorporation of [¹⁴T]leucine into trichloracetic acid-precipitable material and tubulin-enriched fractions, and total tubulin levels as determined by colchicine-binding activity and retention on DE81 filter discs, were measured in various regions of the chick brain following training on a one-trial passive avoidance task, suppression of pecking at a chromed bead as a consequence of the aversive taste of methylanthranilate. Radioactive pulse time was 0.5 h. The only brain region in which changes were found was the anterior forebrain roof, the same area in which biochemical changes in response to exposure of the birds to an imprinting stimulus have been observed previously. In the anterior forebrain roof the changes observed as a consequence of training were detectable at 0.5 and 24 h after the 10-s training experience but not 48 h subsequently. One-half hour after training, there were increases of the order of 20 or 30% in [¹⁴T]leucine incorporation into particulate and postmitochondrial TCA-precipitable material and a tubulin-enriched fraction purified as above. There were comparable increases in the total amount of colchicine-binding activity. By 48 h, none of these increases were detectable. Subcellular fractionation of the particulate fraction showed that most of the increase of incorporation into the tubulin-enriched fraction and in colchicine-binding activity was present in the soluble content of the synaptosomes; there were no increases in either measure in the synaptic membrane fraction. The possible role of changed levels and turnover of tubulin in the plastic responses of the brain to learning experiences is discussed.     

Effective cross sections for production of single-strand breaks in plasmid DNA by 0.1 to 4.7 eV electrons

We determined effective cross sections for production of single-strand breaks (SSBs) in plasmid DNA [pGEM 3Zf(-)] by electrons of 10 eV and energies between 0.1 and 4.7 eV. After purification and lyophilization on a chemically clean tantalum foil, dry plasmid DNA samples were transferred into a high-vacuum chamber and bombarded by a monoenergetic electron beam. The amount of the circular relaxed DNA in the samples was separated from undamaged molecules and quantified using agarose gel electrophoresis. The effective cross sections were derived from the slope of the yield as a function of exposure and had values in the range of 10(-15)- 10(-14) cm2, giving an effective cross section of the order of 10(-18) cm2 per nucleotide. Their strong variation with incident electron energy and the resonant enhancement at 1 eV suggest that considerable damage is inflicted by very low-energy electrons to DNA, and it indicates the important role of pi* shape resonances in the bond-breaking process. Furthermore, the fact that the energy threshold for SSB production is practically zero implies that the sensitivity of DNA to electron impact is universal and is not limited to any particular energy range.     

Phenotypic variability in five <Emphasis Type=Italic>Aceria</Emphasis> spp. (Acari: Prostigmata: Eriophyoidea) inhabiting <Emphasis Type=Italic>Cirsium</Emphasis> species (Asteraceae) in Serbia

From about 250 Cirsium spp., only two Aceria spp. (Acari: Eriophyoidea) have been described, Aceria anthocoptes (Nal.) and Aceria cirsii Pet. B. & Shi. Host specificity, which generally characterizes eriophyoid mites, potentially leads to speciation, so we may expect more than two Aceria spp. and/or other infraspecific taxa. Furthermore, studies on host-related variability in the morphology of Aceria mites are generally lacking. The purpose of this study was to investigate quantitative morphological traits of five Aceria populations inhabiting five Cirsium spp. in Serbia. MANOVA analysis revealed significant differences in 23 commonly used morphological traits as well as four additional traits related to the prodorsal shield design. In addition, the most important qualitative traits using scanning electron microphotographs were studied in order to clarify phenotypic differences among five Aceria spp. Discriminant analysis identified eight traits that significantly differentiate five populations. UPGMA cluster analysis of the squared Mahalanobis distances indicates that A. cirsii was morphologically the most divergent, while A. anthocoptes populations from Cirsium arvense and Aceria sp. from Cirsium heterophyllum were isolated from the branch clustering Aceria spp. populations from Cirsium eriophorum and Cirsium creticum. Analysis of qualitative traits using SEM confirmed results obtained from the analysis of morphometric features.     

The memory enhancing effect of the APP-derived tripeptide Ac-rER is mediated through CRMP2

Photoactivated adenylyl cyclase α (PACα) was originally isolated from the flagellate Euglena gracilis. Following stimulation by blue light it causes a rapid increase in cAMP levels. In the present study, we expressed PACα in cholinergic neurons of Caenorhabditis elegans. Photoactivation led to a rise in swimming frequency, speed of locomotion, and a decrease in the number of backward locomotion episodes. The extent of the light-induced behavioral effects was dependent on the amount of PACα that was expressed. Furthermore, electrophysiological recordings from body wall muscle cells revealed an increase in miniature post-synaptic currents during light stimulation. We conclude that the observed effects were caused by cAMP synthesis because of photoactivation of pre-synaptic PACα which subsequently triggered acetylcholine release at the neuromuscular junction. Our results demonstrate that PACα can be used as an optogenetic tool in C. elegans for straightforward in vivo manipulation of intracellular cAMP levels by light, with good temporal control and high cell specificity. Thus, using PACα allows manipulation of neurotransmitter release and behavior by directly affecting intracellular signaling.