Impact of UV-C Radiation Applied during Plant Growth on Pre- and Postharvest Disease Sensitivity and Fruit Quality of Strawberry.

Ultraviolet-C (UV-C) radiation is efficient in reducing the development of diseases in many species, including strawberry (Fragaria × ananassa). Several studies suggest that UV-C radiation is effective not only because of its disinfecting effect but also because it may stimulate plant defenses. In this study, the effect of preharvest UV-C radiation applied during strawberry cultivation on plant growth, fruit quality, and susceptibility to major fungal diseases such as gray mold, powdery mildew, and soft rot was evaluated. UV-C treatments had an impact on flowering initiation and fruit development. Flowering occurred earlier for UV-C-treated plants than for nontreated plants. At harvest, a larger amount of fruit was produced by treated plants despite their slight decrease in leaf area. UV-C treatment did not improve strawberry shelf life but did not alter the physical integrity of strawberry fruit. Natural infection of leaves to powdery mildew and of fruit to Rhizopus spp. strongly decreased in response to UV-C treatment.

A critical role for VEGF and VEGFR2 in NMDA receptor synaptic function and fear-related behavior.

Vascular endothelial growth factor (VEGF) is known to be required for the action of antidepressant therapies but its impact on brain synaptic function is poorly characterized. Using a combination of electrophysiological, single-molecule imaging and conditional transgenic approaches, we identified the molecular basis of the VEGF effect on synaptic transmission and plasticity. VEGF increases the postsynaptic responses mediated by the N-methyl-D-aspartate type of glutamate receptors (GluNRs) in hippocampal neurons. This is concurrent with the formation of new synapses and with the synaptic recruitment of GluNR expressing the GluN2B subunit (GluNR-2B). VEGF induces a rapid redistribution of GluNR-2B at synaptic sites by increasing the surface dynamics of these receptors within the membrane. Consistently, silencing the expression of the VEGF receptor 2 (VEGFR2) in neural cells impairs hippocampal-dependent synaptic plasticity and consolidation of emotional memory. These findings demonstrated the direct implication of VEGF signaling in neurons via VEGFR2 in proper synaptic function. They highlight the potential of VEGF as a key regulator of GluNR synaptic function and suggest a role for VEGF in new therapeutic approaches targeting GluNR in depression.

Rapid change in the genetic diversity of Botrytis cinerea populations after the introduction of strains in a tomato glasshouse.

In tomato glasshouses, the population structure of airborne inoculum of Botrytis cinerea depends on the production of endogenous inoculum on diseased plants as well as on incoming exogenous inoculum. Both types of inocula may contribute differently to the development of epidemics. Two strains of B. cinerea were introduced in each of four separate compartments of an experimental tomato glasshouse. We monitored their impact on disease development and on the genetic diversity of B. cinerea populations using microsatellite markers. The naturally occurring airborne inoculum of B. cinerea displayed a high level of genetic diversity and was rapidly displaced in the glasshouse, as isolates with microsatellite profiles identical to the introduced strains amounted to 66% of the inoculum sampled from the air 14 days after inoculation and 91% of those collected from stem lesions 60 days after inoculation. This suggested an important role of secondary inoculum in disease development, which is compatible with the hypothesis of a polycyclic development of gray mold epidemics in tomato glasshouses. In controlled-environment tests on tomatoes, a wide range of aggressiveness levels was observed, both for isolates sampled from the air and from lesions on plants. Hypotheses are proposed to explain the negligible impact of naturally incoming isolates on the epidemics observed inside the four glasshouse compartments.

Oidium neolycopersici: intraspecific variability inferred from amplified fragment length polymorphism analysis and relationship with closely related powdery mildew fungi infecting various plant species.

Previous works indicated a considerable variation in the pathogenicity, virulence, and host range of Oidium neolycopersici isolates causing tomato powdery mildew epidemics in many parts of the world. In this study, rDNA internal transcribed spacer (ITS) sequences, and amplified fragment length polymorphism (AFLP) patterns were analyzed in 17 O. neolycopersici samples collected in Europe, North America, and Japan, including those which overcame some of the tomato major resistance genes. The ITS sequences were identical in all 10 samples tested and were also identical to ITS sequences of eight previously studied O. neolycopersici specimens. The AFLP analysis revealed a high genetic diversity in O. neolycopersici and indicated that all 17 samples represented different genotypes. This might suggest the existence of either a yet unrevealed sexual reproduction or other genetic mechanisms that maintain a high genetic variability in O. neolycopersici. No clear correlation was found between the virulence and the AFLP patterns of the O. neolycopersici isolates studied. The relationship between O. neolycopersici and powdery mildew anamorphs infecting Aquilegia vulgaris, Chelidonium majus, Passiflora caerulea, and Sedum alboroseum was also investigated. These anamorphs are morphologically indistinguishable from and phylogenetically closely related to O. neolycopersici. The cross-inoculation tests and the analyses of ITS sequences and AFLP patterns jointly indicated that the powdery mildew anamorphs collected from the above mentioned plant species all represent distinct, but closely related species according to the phylogenetic species recognition. All these species were pathogenic only to their original host plant species, except O. neolycopersici which infected S. alboroseum, tobacco, petunia, and Arabidopsis thaliana, in addition to tomato, in cross-inoculation tests. This is the first genome-wide study that investigates the relationships among powdery mildews that are closely related based on ITS sequences and morphology. The results indicate that morphologically indistinguishable powdery mildews that differed in only one to five single nucleotide positions in their ITS region are to be considered as different taxa with distinct host ranges.

Relationship between Loci conferring downy mildew and powdery mildew resistance in melon assessed by quantitative trait Loci mapping.

ABSTRACT Partial resistance to downy mildew (Pseudoperonospora cubensis) and complete resistance to powdery mildew (Podosphaera xanthii races 1, 2, 3, and 5 and Golovinomyces cichoracearum race 1) were studied using a recombinant inbred line population between 'PI 124112' (resistant to both diseases) and 'Védrantais' (susceptible line). A genetic map of melon was constructed to tag these resistances with DNA markers. Natural and artificial inoculations of Pseudoperonospora cubensis were performed and replicated in several locations. One major quantitative trait loci (QTL), pcXII.1, was consistently detected among the locations and explained between 12 to 38% of the phenotypic variation for Pseudoperonospora cubensis resistance. Eight other Pseudoperonospora cubensis resistance QTL were identified. Artificial inoculations were performed with several strains of four races of Podosphaera xanthii and one race of G. cichoracearum. Two independent major genes, PmV.1 and PmXII.1, were identified and shown to be involved in the simple resistance to powdery mildew. Three digenic epistatic interactions involving four loci were detected for two races of Podosphaera xanthii and one race of G. cichoracearum. Co-localization between PmV.1, resistance genes, and resistance genes homologues was observed. Linkage between the major resistance QTL to Pseudoperonospora cubensis, pcXII.1, and one of the two resistance genes to powdery mildew, PmXII.1, was demonstrated.

Study of the sensitivity of the diabetes-induced pain model in rats to a range of analgesics.

The streptozocin-induced diabetic rat has been put forward as a model of chronic pain with signs of hyperalgesia and allodynia that may reflect signs observed in diabetic humans. The aim of this work was to assess, in streptozocin-induced diabetic rats, the pharmacological activity to several analgesic drugs known to be effective (clomipramine, amitriptyline, desipramine, clonidine, lidocaine), ineffective (aspirin), or with a doubtful effectiveness (morphine) in human painful diabetic neuropathy. The animals were submitted to a mechanical pain test (paw pressure) and the ability of the drugs to reverse diabetes-induced hyperalgesia was tested. The tested antidepressants (0.125-8 mg/kg, i.v.) were slightly effective in diabetic rats; amitriptyline and clomipramine induced a weak effect, whereas desipramine was more active, suggesting noradrenergic specificity. This was confirmed by the effectiveness of clonidine (50, 100, 150 micrograms/kg, s.c.). Lidocaine (1-9 mg/kg, i.v.) had prolonged efficacy on mechanical hyperalgesia. Aspirin (100 mg/kg, i.v.) was without effect and morphine (0.5-4 mg/kg, i.v.) induced a dose-dependent antinociceptive effect but at doses twice as high as those used in normal rats. These results demonstrate the high pharmacological predictivity of this model of painful diabetes and suggest that in this pathological condition, among the drugs acting on monoaminergic transmission, noradrenergic drugs seem the most active.

A new automated method of pain scoring in the formalin test in rats.

The formalin test is a valuable tool widely used in animal pain studies. We offer a new automated technique based on continuous recording of movements of animals injected in a hindpaw with formalin (5%). This method, based on image processing, allows the discrimination of specific pain-induced behaviors and general motor activity. The comparison of the pain scores evaluated by manual and automated methods showed the same biphasic response. This new process was validated by using compounds known to alter pain responses to formalin: morphine and a non-steroidal anti-inflammatory drug (ketoprofen). Morphine dose-dependently usually affects the two phases of formalin response with ED50 of 2.0 +/- 0.5 and 1.5 +/- 0.5 mg/kg s.c. for the first and the second phase, respectively. The injection of ketoprofen significantly decreased pain scores of the second phase but not those of the first phase. The specificity of the method was studied by determining the effect of diazepam. This sedative compound induced a decrease in pain scores as well as a decrease in motor activity parameters. These data show that this automated technique can be considered as a relevant, sensitive and specific tool which allows the easier use of the formalin test especially for the screening of analgesic drugs.

Daily insulin treatment relieves long-term hyperalgesia in streptozocin diabetic rats.

Painful neuropathy is common in human diabetes. In rats, experimental diabetes results in altered pain sensitivity. We examined the effect of chronic insulin treatment on diabetes-induced hyperalgesia in streptozocin diabetic rats. A 20-week period of diabetes resulted in a 62% decrease in paw withdrawal thresholds compared with age-matched normal rats. Daily injections of insulin progressively reversed mechanical hyperalgesia to normal values parallel to the correction of hyperglycaemia. When the treatment was stopped, mechanical hyperalgesia reappeared, but never reached the degree of hyperalgesia observed before insulin treatment, suggesting that indirect mechanisms underlie the effect of normoglycaemia on nociception. The present data suggest that appropriate blood glucose control can help relieve pain in long-term diabetes through indirect mechanisms.

Arbitrarily primed polymerase chain reaction of individual Trichinella specimens.

Recently, 5 sibling species and 3 other phenotypes were identified in the genus Trichinella. Single primers of arbitrary nucleotide sequence were used to produce random amplified polymorphic DNA starting from decreasing amounts of Trichinella spiralis and Trichinella britovi DNA. Reproducible amplification products from 30 pg of DNA were obtained using 1 of 6 examined primers. These fragments distinguish between 2 European Trichinella species, T. spiralis, showing a 1,350-bp band, and T. britovi, showing 400- and 1,100-bp bands. The developed procedure allows the characterization of crude DNA preparations of single muscle-stage larvae, avoiding time-consuming passages of parasites in laboratory animals.

Effect of intrathecal serotonin on nociception in rats: influence of the pain test used.

The involvement of serotonin (5-HT) in the modulation of nociceptive impulse in the spinal cord has been widely studied. However, its activity, considering the nature of noxious stimuli and the type of 5-HT receptors involved, merits to be further elucidated. The present behavioural study was performed to compare the dose-antinociceptive effect relationship of 5-HT in rats, after intrathecal (i.t.) injection (10 microliters/rat), using mechanical (paw pressure), thermal (tail immersion and tail-flick) and chemical (formalin) pain tests. In rats submitted to the paw pressure test, 5-HT was found to possess a dose-dependent antinociceptive activity (0.01, 0.1, 1, 10 and 20 micrograms/rat) when vocalization threshold was assessed as a pain parameter. A peak effect occurred 5 min after the injection and the effect was maintained for 45 min. The lowest active dose was 0.1 microgram (maximum increase in vocalization thresholds, 23 +/- 3%) and a plateau was observed for 10 micrograms and 20 micrograms (maximum increase in vocalization thresholds, 72 +/- 7% and 71 +/- 6%, respectively). When paw withdrawal was assessed, 5-HT induced a weak hyperalgesic effect for the highest dose (60 micrograms), while other doses were ineffective. In the tail-immersion (warmth and cold) and tail-flick tests, different doses (0.01, 0.1, 1, 10, 30, 60 and 100 micrograms/rat) were studied. In the two immersion tests, only the highest doses (60 micrograms and 100 micrograms) significantly increased the withdrawal thresholds from 5 to 45 min after the injection. The maximum effect was observed at 5 min (23 +/- 4% and 21 +/- 6% for 60 micrograms; 27 +/- 3% and 30 +/- 6% for 100 micrograms in the warmth and cold immersion test, respectively). In the tail-flick test, the doses of 30, 60 and 100 micrograms/rat dose-dependently and significantly increased the withdrawal thresholds from 5 to 45 min after the injection, with a maximum effect at 5 min (30 +/- 5% for 30 micrograms; 37 +/- 6% for 60 micrograms; and 45 +/- 4% for 100 micrograms). In the formalin test, 5-HT (10, 25, 50, 75 and 100 micrograms/rat) produced dose-related antinociception. The nociceptive response (licking of the injected paw) was significantly reduced from 25 micrograms (-59 +/- 11%) in the early phase, whereas the lowest active dose in the late phase was 50 micrograms (-46 +/- 17%). For both phases, a total inhibition was obtained with 100 micrograms. It is concluded that the effect of 5-HT on pain tests may differ according to the applied stimulus and the parameter assessed; unspecific effects of 5-HT may modify motor reactions to noxious stimuli. Mechanical test (assessment of vocalization) was the most sensitive to 5-HT. These observations are of importance in order to further study the pharmacological mechanisms involved in 5-HT spinally induced antinociception.

Is the reduced efficacy of morphine in diabetic rats caused by alterations of opiate receptors or of morphine pharmacokinetics?

Because it generally is admitted that neuropathic pain is resistant to opioid analgesia, we investigated the effect of morphine on hyperalgesia in streptozocin-induced diabetes in rats. The antinociceptive effect of morphine (0.5-4 mg/kg i.v.) on mechanical (paw pressure test), thermal (tail immersion test) and chemical (formalin test) hyperalgesia was reduced. To clarify the mechanisms involved in the alteration of morphine analgesia, the binding characteristics of mu and delta receptor agonists and the pharmacokinetics of morphine and its glucuronide metabolites morphine 3-glucuronide and morphine 6-glucuronide were determined. KD and Bmax values for [3H][D-Ala2,(Me)Phe4, Gly(ol)5]enkephalin and [3H][D-Pen2,D-Pen5]enkephalin to cerebral mu and delta opiate receptors were not altered by diabetes. Likewise, the plasma maximal concentration of morphine and metabolites, as well as the area under the curve, did not differ between diabetic and normal rats. Only the total clearance and the apparent volume of distribution of morphine were increased in diabetic rats, which suggests that the diabetes-induced glycosylation of proteins might increase the distribution of morphine in the aqueous compartment. These data indicate that the reduced analgesic effect of morphine caused by diabetes cannot be explained by a decrease in opiate-receptor affinity or density but rather by kinetic alteration of morphine (increase of total clearance and of volume of distribution in comparison with healthy animals).

Random amplified polymorphic DNA fingerprints of the eight taxa of Trichinella and their comparison with allozyme analysis.

Eight taxa have recently been proposed as being encompassed by the genus Trichinella on the basis of allozyme and biological data. In this paper we show that an analogous 8 taxon structure for this genus results from the random amplified polymorphic DNAs (RAPDs). Five 10-mer or 20-mer primers were used under different polymerase chain reaction (PCR) conditions to produce multiband RAPD fingerprints from muscle larvae of 40 isolates of Trichinella spp. The resulting RAPD data were analysed following the numerical taxonomic approach, and the resulting classification was compared to that derived from allozyme data. The agreement found between allozymes and RAPDs, while supporting the polyspecific structure of the genus Trichinella, confirms the potential of RAPDs as a tool for the detection of cryptic species. The selected primers were tested on individual muscle larvae in an attempt to standardize a RAPD assay for the routine identification of the 8 taxa of Trichinella. Only 1 of the 5 primers yielded reproducible fingerprints from the single larvae. Using this primer, the 5 species and the 3 other taxa of the genus Trichinella can be identified in a single assay without the need for massive in vivo parasite production.

QTLs for resistance to powdery mildew in pepper under natural and artificial infections.

Epidemics of powdery mildew due to Leveillula taurica is an increasing problem in pepper production areas, particularly in coastal regions or greenhouse cultivation. The highly resistant genitor 'H3' was submitted to genetic analysis and QTL mapping in order to promote the introgression of its oligogenic resistance into large and sweet-fruited cultivars. The doubled-haploid progeny from the cross 'H3' (resistant) by 'Vania' (susceptible) was tested for resistance under both natural field infection and artificial inoculation tests, and QTL detection was compared for those two methods. Seven genomic regions including additive QTLs and epistatic interactions were detected, explaining altogether the major part of genotypic variance. Two genomic regions were common to both the evaluation methods, whereas other QTLs were method-specific, reflecting the environment dependence of powdery mildew epidemics. Orthologies with tomato genomic regions carrying resistance genes to L. taurica and Oidium lycopersicum were revealed by comparative mapping with pepper. Tight linkages between the detected QTLs and virus resistance or fruit color traits in pepper were also shown, which adds to the agronomic importance of these regions in pepper breeding programs.

RAPD fingerprinting is useful for identification of Azospirillum strains.

In vitro amplification of genomic DNA fragments with single primers of arbitrary sequence was used as a rapid and sensitive method to obtain fingerprints of ten strains belonging to three of the Azospirillum species: brasilense, lipoferum and amazonense. Each strain showed a distinctive pattern of bands that permitted its unequivocal identification. Closely related strains produced almost identical fingerprints. Pairwise comparison and cluster analysis of the amplification patterns allowed grouping of the strains. The resulting dendrograms are similar to previous dendrograms based on the restriction endonuclease analysis (REA) of total DNA and on the restriction fragment length polymorphism (RFLP). Our results indicate that the random amplified polymorphic DNA (RAPD) technique is a simple, fast and useful tool for the determination of genetic relationships among Azospirillum isolates and to evaluate the genomic stability of the Azospirillum strains released in the environment.