Functional analysis of the Alternaria brassicicola non-ribosomal peptide synthetase gene AbNPS2 reveals a role in conidial cell wall construction

Alternaria brassicicola is a necrotrophic pathogen causing black spot disease on virtually all cultivated Brassica crops worldwide. In many plant pathosystems fungal secondary metabolites derived from non-ribosomal peptide synthetases (NPSs) are phytotoxic virulence factors or are antibiotics thought to be important for niche competition with other micro-organisms. However, many of the functions of NPS genes and their products are largely unknown. In this study, we investigated the function of one of the A. brassicicola NPS genes, AbNPS2 . The predicted amino acid sequence of AbNPS2 showed high sequence similarity with A. brassicae , AbrePsy1, Cochliobolus heterostrophus , NPS4 and a Stagonospora nodorum NPS. The AbNPS2 open reading frame was predicted to be 22 kb in length and encodes a large protein (7195 amino acids) showing typical NPS modular organization. Gene expression analysis of AbNPS2 in wild-type fungus indicated that it is expressed almost exclusively in conidia and conidiophores, broadly in the reproductive developmental phase. AbNPS2 gene disruption mutants showed abnormal spore cell wall morphology and a decreased hydrophobicity phenotype. Conidia of abnps2 mutants displayed an aberrantly inflated cell wall and an increase in lipid bodies compared with wild-type. Further phenotypic analyses of abnps2 mutants showed decreased spore germination rates both in vitro and in vivo , and a marked reduction in sporulation in vivo compared with wild-type fungus. Moreover, virulence tests on Brassicas with abnps2 mutants revealed a significant reduction in lesion size compared with wild-type but only when aged spores were used in experiments. Collectively, these results indicate that AbNPS2 plays an important role in development and virulence.     

Numerical taxonomy of Bacillus isolated from orally administered drugs

Numerical taxonomy procedures were used to study 118 strains of Bacillus isolated from non-sterile drugs prepared for oral administration. Similarities between pairs of strains were calculated by the simple matching coefficient of Sokal and Michener (S_SM). Each strain was tested for 60 unit characters and three clusters were defined. The strains in each cluster presented a similarity level of at least 60%. Cluster A comprised the strains identified as Bacillus cereus (S_SM= 93·13%), cluster B contained three subgroups corresponding to the species B. pumilus, B. subtilis and B. licheniformis (S_SM= 84·35%) and cluster C also included three subgroups that belonged to the species B. firmus, B. lentus and B. badius (S_SM= 80·14%). The most discriminating tests were selected to differentiate the clusters from the subgroups. The feature with the highest discriminating power between clusters A and B was the lack of acid production from arabinose and mannitol. The Voges-Proskauer, methyl red tests and sensitivity to polymyxin B clearly distinguished cluster A from C. The Voges-Proskauer test and acid production from arabinose were the best to differentiate between B and C. Bacillus pumilus and B. subtilis differed in starch hydrolysis and B. licheniformis in growing anaerobically. To discriminate B. firmus from B. lentus the most important tests were the acid production from glucose and sucrose; intermediate strains were found. Bacillus badius was differentiated from B. firmus by 10 tests, and from B. lentus by the production of urease.     

Synaptosome Antisera affect Permeability of Synaptosomal Membranes <Emphasis Type="Italic">in vitro</Emphasis>

ANTISERA against specific regions of the brain can specifically influence the electrical activity of those regions^1,2. It is possible that these immunological techniques may be used to determine the role of specific chemical components in brain function.     

Effects of Ca2+ and Temperature on Potassium Uptake along Roots of Wheat, Rice and Cucumber

The differences in K⁺ uptake of different segments of excised roots of two thermophilic plants (rice, Oryza sativa L. cv. Dunghan Shali and cucumber, Cucumis sativus L. cv. Csemege Fürtös) and a non-thermophilic plant (wheat, Triticum aestivum L. cv. Aurora) were investigated in the presence and absence of Ca²⁺, at 0 and 25°C, using radiotracer K⁺(⁸⁶Rb⁺) technique. The K⁺ uptake exhibited different temperature- and Ca²⁺-dependent distributions along the root axis for the different species studied. In the case of rice and cucumber an extraordinarily large K⁺ uptake occurred in the apical root portion at 0°C if Ca²⁺ was omitted. The presence of Ca²⁺ diminished this anomaly. For wheat normal K⁺ uptake patterns were observed under similar conditions. At 25°C Ca²⁺-stimulated K⁺ uptake may appear in each root segment, depending upon species and composition of the uptake solution. The results indicate that there may be considerable differences in the compositions of the cell walls and membranes of root cells of thermophilic and non-thermophilic plants, and in their ion-exchange properties, especially in the apical region.     

Effects of Ca2+ and Temperature on K+ Content Distribution along Roots of Wheat, Rice and Cucumber

The effects of Ca²⁺ and temperature on the K⁺ contents of root segments of wheat (Triticum aestivum L. cv. Aurora), rice (Oryza sativa L. cv. Dunghan Shali) and cucumber (Cucumis sativus L. cv. Csemege Fürtös) were investigated with special regard to the low-temperature anomaly of the K⁺ uptake of thermophilic plants. The anomaly occurred in those root segments where the K⁺ contents turned out to be highest. The K⁺ contents of the apical root sections of thermophilic species responded in general to Ca²⁺ in more pronounced ways than those of wheat, at both 0 and 25°C. The concerted actions of a purely physical process with negative temperature coefficient and of the special thermotropic properties of the membranes are suggested to be responsible for the low-temperature anomaly. A strict discrimination between the Viets-effect on the content (classical Viets-effect) and on the uptake is proposed. The classical Viets-effect seems to be related to alterations in both active transport and exchange processes.     

Comparative Physiology of Neurohypophysial Hormone Action on the Vertebrate Oviduct-Uterus

The neurohypophysial hormone, arginine vasotocin, is depletedfrom the hypothalamus, and rises in concentration in the bloodduring oviposition in hens. The contractile responses of isolatedoviducts from birds, reptiles and amphibians are more sensitiveto arginine vasotocin than to oxytocin or mesotocin. This evidenceclearly indicates that arginine vasotocin is involved in parturitionor oviposition in nonmammalian tetrapods. Evidence for a physiologicalrole for specific neurohypophysial hormones in the regulationof oviduct—or in some cases ovarian — contractilityin fishes is unclear and occasionally contradictory. However,it appears unlikely that arginine vasotocin is involved in thefish species that have been investigated. It is evident that,much like the neurohypophysial hormones, the neurohypophysialhormone receptors of the vertebrate myometrium have undergoneevolutionary change.