Changes in Wheat Leaf Extracellular Proteolytic Activity after Infection with Septoria tritici

The proteolytic activity of the leaf extracellular space of wheat cultivars Pigüé and Isla Verde was estimated after inoculation of either detached leaves or plants with the fungus Septoria tritici. Pigüé is resistant, whereas Isla Verde is susceptible to the disease caused by S. tritici. Viable conidiospores of the fungus caused similar increases in both hydrogen peroxide production and chitinase activity of the cultivars studied. In contrast, they caused a decrease in the extracellular serine proteinase activity of Isla Verde and a significant increase in that of Pigüé. Independently of the cultivar from which it was extracted, the extracellular serine proteinase inhibited the germination of Septoria tritici conidiospores. These results suggest that the proteolytic activity of the leaf extracellular space can participate in the defence of wheat plants against Septoria tritici. Its regulation may be controlled by specific defence components of each cultivar.     

Seasonal and interannual variation in the energetic condition of adult male Atlantic sharpnose shark Rhizoprionodon terraenovae in the northern Gulf of Mexico

One hundred and thirty Atlantic sharpnose shark Rhizoprionodon terraenovae livers were collected from April 1999 to October 2001 from inshore waters of the Mississippi Sound to investigate seasonal and inter‐annual variation in their energetic condition. A decline in the hepato‐somatic index ( I _H) was observed from 1999 to 2001. In addition, I _H, liver specific energy content and total energy content were lowest during the summer and highest during the spring and autumn, while liver water content was highest during the summer and lowest during the spring and autumn.     

Foraging behaviour influences the outcome of predator–predator interactions

Abstract.  1. Interactions among predators may influence the total efficiency of a predator complex. The effect of intra- and interspecific interactions of the generalist predators Orthotylus marginalis (Heteroptera: Miridae) and Anthocoris nemorum (Heteroptera: Anthocoridae) was investigated in a laboratory experiment. Outcomes of the interactions were determined by comparing predation rates on eggs and larvae of the blue willow beetle Phratora vulgatissima of single individuals with those of two individuals of the same or different species.
2. A non-additive, antagonistic effect on predation rates due to intraspecific interactions was found between individuals of A. nemorum . No such effect was found in O. marginalis . These results are as expected as a consequence of differences in behaviour of the two predator species: A. nemorum is a much more active and mobile predator than O. marginalis .
3. Contrary to expectation, interspecific interactions between A. nemorum and O. marginalis did not affect the total predation rate.
4. An observation from the field corroborated the results obtained in the laboratory study; there was no negative relationship between the densities of the two predator species, indicating that the two species do not interact negatively in the field at their natural densities.
5. It is concluded that the additive effect of multiple predator species is of potential value in biological control.     

Location and distribution of symbiotic bacteria during floral development in Ardisia crispa

Abstract. The location and distribution of symbiotic bacteria during floral development in Ardisia crispa (Thunb.) A.DC., a species characterized by bacterial leaf nodules, has been studied using light, scanning and transmission electron microscopy. During early floral development, bacteria in mucilage derived from host plant trichomes, become enclosed in a small conical chamber on top of the placenta, as a result of the closure and fusion of the carpel initials. The placental epidermal cells, which appear to be secretory in nature, become detached apically in places forming a network of grooves which traverse the placental surface. The symbiotic bacteria are preferentially located in these grooves. As growth and development of the placenta proceed, the grooves widen and deepen to form channels. The cells lining these channels secrete a mucilaginous material. The network of channels covers the entire placental surface and terminates at the placental margins surrounding the ovules. Bacteria are found within the channels, at the ends of the channels near the margin of the placenta, on the surface of the ovules and in the micropyle. It is suggested that these mucilage-filled channels are responsible for, and a prerequisite of, ensuring that the bacterial partner is efficiently transmitted from one host generation to the next by providing a mechanism by which the bacteria arc accurately placed within the developing seed.     

Distribution of elements in rabbit liver lobule

The elemental composition of rabbit liver was determined by the PIXE and micro-PIXE methods. The mean concentrations of P, S, Cl, K, Fe, Cu, Zn, and Rb measured by both methods were similar. The latter method also allowed for localization of elements within lobule territory. It has been found that some elements are more prevalent in the veins (Cl, Fe) and others in the liver parenchyma (P, Cu, Zn). Moreover, Zn showed the characteristic intralobular distribution. Some methodological aspects of microbeam application to biological materials were also discussed.     

Developmental biochemistry of cottonseed embryogenesis and germination. XIX. Sequences and genomic organization of the α globulin (vicilin) genes of cottonseed

The globulin storage protein genes of cotton are found to exist as gene tandems that contain a gene from each of the 2 globulin subfamilies separated by a spacer region of about 2700 or 3400 base pairs. Three different tandems have been identified by restriction endonuclease mapping of genomic DNA. A cDNA that is different from the genes of the tandems in map sites and/or in nucleotide sequence indicates that a fourth tandem probably exists in the cotton genome. Since the species of cotton used here (Gossypium hirsutum) is an amphidiploid, it is likely that two of the tandems are contributed from each genome.Considerable divergence in nucleotide sequence (18%) and in derived amino acid sequence (28%) is found when the 2 genes of a sequenced tandem are compared. The sequence of the cDNA closely resembles one of the genes in the tandem showing only a 4% divergence in nucleotides and a 4.2% divergence in amino acids. Thus the 2 genes of each tandem represent a relatively ancient gene duplication that has given rise to the two globulin subfamilies of cotton. Only one subfamily has a glycosylation site and the glycosylation of its derived proteins gives rise to the 2 molecular weight sets of globulins seen on gel electrophoresis.Other basic features of these genes and their derived proteins are presented.