Semiochemical strategies for sea louse control: host location cues

The development of behavioural bioassays and electrophysiological recording techniques has enabled the role of semiochemicals to be investigated for the first time in Lepeophtheirus salmonis (Kr?yer). Adult male sea lice L salmonis were activated by, and attracted to, salmon-conditioned water (SCW) and SCW extract. Non-host fish odours, turbot-conditioned water (TCW) and turbot-conditioned water extract (TCW extract), elicited activation but no attraction in the lice. Solid-phase extraction techniques were developed to extract low molecular weight components of fish odours, and biological activity was shown to be confined to these. Electrophysiological activity from aesthetascs in the first antennae was found and neural responses to odours were recorded from the antennal nerves. Preliminary experiments on individual chemicals (isophorone, 1-octen-3-ol) linked to salmon revealed behavioural activation and electrophysiological responses in adult male L salmonis. Isophorone was shown to be significantly attractive to sea lice when placed in a slow-release system in a perfused tank of seawater in a choice situation. Proof of concept has been established for successfully extracting odour cues from seawater, analysing their biological activity and applying these to slow-release technologies for field trapping of lice. Future work involving linked GC-MS techniques using behaviour, electrophysiological responses, and organolepsis will establish further host location cues specific to Atlantic salmon.     

Histology, Ultrastructure and Carbohydrate Histochemistry of Pig Carpal Glands

The morphological differences between two types of secretory cells (clear and dark) from pig carpal glands were examined. The main difference is the presence in the dark cells of secretory granules of moderate electron density, made up of acidic and neutral glycoproteins. The possible functional purposes of the carpal glands and of glycogen present in both cell types are also discussed.     

Nitric oxide in bovine corpus luteum: Possible mechanisms of action in luteolysis

Although prostaglandin (PG) F_2α is considered as the principal luteolytic factor, its action on the bovine corpus luteum (CL) is mediated by other intraovarian factors. Among them, nitric oxide (NO) seems to play a mandatory role in luteolysis. In this article we review the background and current status of work on possible roles of NO in the CL function, based on available information and our own experimental data. NO is produced in all three main types of bovine CL cells: steroidogenic, endothelial and immune cells. PGF_2α and some luteolytic cytokines (tumor necrosis factor, interferon) increase NO production and stimulate NO synthase expression in the bovine CL. NO inhibits progesterone production, stimulates the secretion of PGF_2α and leukotriene C4, reduces the number of viable luteal cells and, finally, participates in functional luteolysis. NO induces the apoptotic death of CL cells by the modulation of bcl‐2 family gene expression and the stimulation of caspase‐3 gene expression and activity. However, this simple molecule shows both luteolytic and luteotropic actions during the estrous cycle in ruminants. The aim of this overview is to present and discuss the recent findings crucial for understanding NO role in the process of CL regression in cattle.     

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Molecular subtype-specific clinical diagnosis of prion diseases

Sporadic Creutzfeldt-Jakob disease (sCJD) is a rare transmissible disease caused by accumulation of pathological prion protein (PrP(sc)) in the CNS. According to the codon 129 polymorphism (methionine or valine) and the prion protein type 1 or 2, a classification into distinct subtypes was established. Further analysis of these subtypes detected atypical clinical forms with longer disease duration or younger age at onset. The CJD subtype influences sensitivity of the technical investigations such as 14-3-3 in CSF, periodic sharp wave complexes in the EEG or hyperintense basal ganglia in MRI. A further characterization of these subtypes is important for reliable diagnosis and identification of rare disease variants. The aim is to establish specific patterns of test results and clinical findings. These improvements in diagnostics may be the reason for the apparent increase in sCJD incidence in Germany from 0.9 in 1994 to 1.6 in a million in 2005. Despite careful surveillance, no patient with variant CJD has been detected to date in Germany. Here we present the data of the CJD surveillance of the last 13 years. Additionally, the improvements in diagnostics and differential diagnosis are discussed.     

Occurrence, inheritance and use of reproductive mutants in alfalfa improvement

The widespread occurrence of 2ngametes (i.e. gametes with the somatic chromosome number) in the Medicago sativa-coerulea-falcata complex supports the concept that gene flow from diploid to tetraploid species occurs continuously in nature and plays a key role in alfalfa evolution. Breeders realized early that gene transfer between ploidy levels via 2n pollen and 2n eggs would have had potential use in cultivated alfalfa improvement. Cytological investigations provided insights into the types of meiotic abnormalities responsible for the production of 2n gametes. Alterations were defined as genetically equivalent to first (FDR) or second division restitution(SDR) mechanisms. For breeding purposes,data have proven that 2n gametes of the FDR type are more advantageous than those obtained by SDR for transferring parental heterozygosity and retaining epistatic interactions. The use of diploid meiotic mutants that produce 2ngametes is now recognized as one of the most effective methods available for exploiting heterosis and introgressing wild germplasm traits into cultivated tetraploid alfalfa via unilateral (USP) and bilateral sexual polyploidization (BSP) schemes. Both2n egg and 2n pollen producers could be used for direct gene transfer from wild diploid relatives into cultivated alfalfa by means of 2x-4x and4x-2x crosses. Although data have shown that forage yield improvement can be achieved when plants are sexually tetraploidized, problems related to reduced plant fertility and seed production remain largely unexplained. Apomixis has the potential of cloning plants through seed and thus provides a unique opportunity for developing superior tetraploid cultivars with permanently fixed heterosis and epistatic effects. A main goal in alfalfa breeding could be the introduction of functional apomixis (i.e. Apomeiosis and parthenogenesis) in cultivated alfalfa stocks. In the future, the efficiency of alfalfa breeding programs based on the use of reproductive mutants could be improved by direct selection at the genotype level using RFLPs and PCR-based markers. Suitable DNA markers and detailed linkage maps of alfalfa mutants should help to discover apomictic mutants and address basic genetic issues such as the extent of genomicre combination in polyploid hybrids and the effect of sexual polyploidization on heterosis. Molecular markers have recently been used in alfalfa for studying the inheritance of 2n gamete formation and identifying polymorphisms associated to genes involved in meiotic abnormalities. Molecular tagging of 2n egg and 2n pollen formation not only should explain the genetic control and regulation of these traits, but may also be an essential step towards marker-assisted selection of 2n gamete producers and implementation of USP and BSP breeding schemes. Future perspectives include strategies for the map-based cloning of genomic DNA markers,and screening of EST mini-libraries related to flowers at different developmental stages from meiotic mutants and wild-type scan lead to the identification of mRNAs and thus of candidate genes that control 2n gamete formation in alfalfa. This revised version was published online in July 2006 with corrections to the Cover Date.     

Concentration of benzoxazinoids in roots of field-grown wheat (Triticum aestivum L.) varieties

Benzoxazinones are naturally occurring secondary metabolites of some Gramineae plants, responsible for their resistance to some pathogenic fungi and for their allelopathic action. Six varieties of winter wheat grown in fields under organic or conventional systems and 11 old accessions were tested for two consecutive seasons and three plant development stages for the concentration in their roots of cyclic hydroxamic acids and their degradation products. This is the first report of six benzoxazinones analyzed in plants grown in the field. An analytical technique employing LC-DAD was used for determination. It was shown that 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one, its degradation product 6-methoxybenzoxazolin-2-one, and the lactam 2-hydroxy-7-methoxy-1,4-benzoxazin-2-one were predominant compounds in all tested samples. Their concentrations significantly differed with plant development stage and season, but no significant differences were found between varieties and between plant cultivation systems. The concentrations of 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA) and its degradation product benzoxazolin-2-one (BOA) were much lower, ranging from 60 to 430 mg/kg of dry matter, depending on accession, stage of development, and season. There was no significant difference found between plants grown in different cultivation systems, but there were significant differences between old and new varieties; concentrations of DIBOA and its derivatives were significantly lower in old accessions. It was concluded that the concentrations of DIBOA and BOA, which are precursors of highly fungicidal 2-aminophenol, 2-amino-3H-phenoxazin-3-one, and 2-acetylamino-3H-phenoxazin-3-one, are theoretically high enough to protect plants against some soilborne pathogens.     

Silencing of G1-1 and A2-1 genes. Effects on general plant phenotype and on tuber dormancy inSolanum tuberosum L.

Summary We have evaluated the effect that the, silencing of two genes specifically expressed in conditions of dormancy (A2-1) and sprouting (G1-1) had on tuber dormancy. For this purpose potato plants (Solanum tuberosum L. cv. Désirée) were transformed with the antisense of the genes G1-1 and A2-1 under the control of constitutive 35S CaMV promoter. A first generation of transgenic plants was propagated from axenic stem cuttings and a second generation by tuber planting. The plants obtined were analyzed for the length of dormancy, plant morphology and agronomic characteristics. Statistical analysis of dormancy in lines obtained from the original transformants for the antisense of G1-1 gene showed a significant increase in length as compared with different types of control plants, with few effects on plant vegetative habit and tuber production. In contrast, results obtained on A2-1 antisense transformed plants did not reveal any significant change on the length of dormancy. Here we report small-scale field trials performed with the aim to select and regenerate commercially exploitable potato plants with a stable transgene-dependent phenotype, affecting the length of dormancy.