Analysis of a Secreted Aspartic Peptidase Disruption Mutant of Glomerella cingulata

Peptidases have been implicated in the pathogenicity of fungi that cause disease in plants. Expression of the secreted aspartic peptidase gene (gcsap), of a Glomerella cingulata isolate pathogenic on apples, is induced during appressorium formation. To determine whether the secreted aspartic peptidase (GcSAP) is essential to pathogenicity, gcsap was disrupted using a vector containing a 637 bp fragment of genomic DNA that encodes the sequence spanning the two active site aspartic acid (Asp) residues. To ensure that the truncated gcsap gene products could not have residual peptidase activity the codons for the active site residues Asp¹¹² and Asp²⁹⁷ were both mutated to histidine residues. Both PCR and Southern analysis confirmed disruption of gcsap. Neither gcsap mRNA nor GcSAP activity was detected in the disruption mutant. Pathogenicity tests on fruit from three apple cultivars showed that GcSAP was not required for pathogenicity. The disruption mutant grew on medium containing protein as the sole source of nitrogen because G. cingulata secretes a previously undetected peptidase(s). A serine peptidase that had a pH optimum between pH 7.0 and 8.0 and a K _m of 0.25 mM for the synthetic substrate succinyl-Ala–Ala–Pro–Phe-p-nitroanilide was identified.     

The Effect of Inoculation Treatment and Long-term Application of Moisture on Fusarium Head Blight Symptoms and Deoxynivalenol Contamination in Wheat Grains

Fusarium head blight (FHB) is an important disease of wheat, which can result in the contamination of grains with mycotoxins such as deoxynivalenol (DON). Artificial inoculation of flowering ears with conidial suspensions is widely used to study FHB diseases. Our goal was to compare four inoculation treatments in which a conidial suspension was sprayed on flowering ears and to study the effect of the application of moisture during kernel setting and filling with a mist-irrigation system. Ten wheat genotypes were inoculated with a DON-producing Fusarium culmorum strain. Inoculation treatments varied in time of application of the inoculum (morning or evening) and in the method of controlling humidity during inoculation (bagging or mist irrigation). A wet season was simulated with a mist-irrigation system, keeping the crop canopy wet for at least 26 days after flowering. The severity of FHB symptoms (area under disease progress curve (AUDPC)), yield loss and DON contamination in the grains were determined. AUDPC data obtained with the different inoculation treatments were highly correlated (r=0.85–0.95). Mist irrigation after inoculation resulted in a higher mean disease severity, but in a overall lower toxin contamination as compared to the non-irrigated treatments. Genotypic differences in DON accumulation were present: for one wheat line toxin contamination significantly increased when irrigated, while two genotypes accumulated significantly less toxin. The closest relationships (r=0.73–0.89) between the visual symptoms and the DON content were obtained under moderate mean infection pressure. This relation between visual symptoms and the DON content deteriorated at higher infection levels.     

Effectiveness of the resistance inducer prohexadione‐Ca against fireblight in shoots of apple trees inoculated with Erwinia amylovora1

Due to the lack of effective, non‐phytotoxic and publicly acceptable materials for controlling fireblight in pome fruit trees, novel strategies against Erwinia amylovora are being sought. Resistance‐inducing compounds, such as prohexadione‐Ca, represent promising alternatives. Prohexadione‐Ca is the active substance of the bioregulator Regalis, currently being introduced in several European countries and overseas. Prohexadione‐Ca reduces shoot elongation due to inhibition of gibberellin biosynthesis. Furthermore, it leads to significant changes in the spectrum of flavonoids and their phenolic precursors in pome fruits, which causes reduced susceptibility to fireblight and other pathogens. In 2002 and 2003, container‐grown apple trees of the cultivars ‘Idared’ and ‘Freedom’ were treated with different dosages of prohexadione‐Ca two weeks before inoculation with E. amylovora. The effect of prohexadione‐Ca against shoot blight was determined by measuring the lengths of necrotic lesions and symptoms on vascular bundles caused by the pathogen. Treatments with prohexadione‐Ca turned out to be much superior to the ones with streptomycin, kasugamycin and a bacterial antagonist, which were used for comparison. Acibenzolar‐S‐methyl (Bion), another resistance‐inducing compound, was included in some of the experiments and gave intermediate results. The simultaneous control of excessive shoot growth and shoot infections by fireblight is seen as a major advantage of using prohexadione‐Ca in pome fruit trees.     

Identification of irisin immunoreactivity in porcupine (Hystrix cristata) adrenal glands and kidneys

Irisin, a novel peptide, was initially been shown to be expressed explicitly in the muscle tissues. We studied the presence of irisin immunoreactivity in porcupine adrenal glands and kidneys. Immunocytochemistry showed that irisin was localised both in the adrenal cortex and adrenal medulla. In organs, irisin immunoreactivity was found in the tubular and collecting system of the nephron. The functional role of irisin in the adrenal gland and kidney has not been precisely yet. However, irisin might have a paracrine and autocrine function as do other locally produced peptides.     

Congenital duodenocolic fistula in a dog

A one‐year‐old female cocker spaniel presented with a 6‐month history of persistent diarrhoea. Abdominal ultrasonographic examination revealed mild diffuse thickening of the intestinal wall coupled with mesenteric lymphadenopathy. A connection between the duodenum and the colon was observed during an endoscopic procedure and confirmed by computed tomography. Surgical resection of the communication allowed remission of the diarrhoea. Histology showed a normal duodenal epithelium and muscular layer. A duodenocolic fistula is an abnormal connection within the digestive tract, which in humans is usually considered a complication of a local pathological condition. Due to the absence of a predisposing cause and, in view of the dog's age and histological results, a congenital origin was suspected.