Evidence that Northern Pioneering Pines with Tuberculate Mycorrhizae are Unaffected by Varying Soil Nitrogen Levels

Tuberculate mycorrhizae on Pinus contorta (lodgepole pine) have previously been shown to reduce acetylene, but an outstanding question has been to what degree these structures could meet the nitrogen requirements of the tree. We compared the growth, tissue nitrogen contents, and stable nitrogen isotope ratios of P. contorta growing in gravel pits to the same species growing on adjacent intact soil. Trees growing in severely nitrogen deficient gravel pits had virtually identical growth rates and tissue nitrogen contents to those growing on intact soil that had nitrogen levels typical for the area. δ¹⁵N values for trees in the gravel pits were substantially lower than δ¹⁵N values for trees on intact soil, and isotope ratios in vegetation were lower than the isotope ratios of the soil. The form of soil nitrogen in the gravel pits was almost exclusively nitrate, while ammonium predominated in the intact soil. Discrimination against ¹⁵N during plant uptake of soil nitrate in the highly N-deficient soil should be weak or nonexistent. Therefore, the low δ¹⁵N in the gravel pit trees suggests that trees growing in gravel pits were using another nitrogen source in addition to the soil. Precipitation-borne nitrogen in the study area is extremely low. In conjunction with our other work, these findings strongly suggests that P. contorta and its microbial symbionts or associates fix nitrogen in sufficient amounts to sustain vigorous tree growth on the most nitrogen-deficient soils.     

Somatostatin-detergent interaction

The effect of cationic, anionic and nonionic detergents on the EPR spectrum of spin-labeled somatostatin has been studied. At detergent concentrations well above the critical micelle concentration, nonionic detergents do not alter the EPR spectrum. Sodium dodecyl sulfate markedly alters both the line height ratio and the hyperfine splitting constant, whilst dodecyltrimethylammonium bromide alters only slightly the hyperfine splitting constant and line height ratio. The somatostatin-sodium dodecyl sulfate complex appeared monodisperse by sedimentation equilibrium with about 17 g bound detergent per g peptide. Circular dichroic and difference spectra of the dodecyl sulfate-somatostatin complex show that the tryptophanyl residue is buried in a nonpolar environment and that the secondary and tertiary structure of the peptide is markedly altered. Sedimentation equilibrium studies suggest that two types of dodecyltrimethylammonium-somatostatin complex exist. One type resembles the dodecyl sulfate-peptide complex, whilst the other appears to include several peptide units with only about one gram bound detergent per gram peptide.     

Plant phosphoglucose isomerase genes lack introns and are expressed in Escherichia coli

Nuclear genes that appear to encode both cytosolic and plastid isozymes of phosphoglucose isomerase (PGI), an essential glycolytic enzyme, have been isolated from three diploid species of the annual wild flower genus Clarkia (Onagraceae). The genes do not contain introns and are expressed to varying degrees in Escherichia coli when cloned in either Charon 35 phage or pUC plasmid vectors. The PGI proteins synthesized in E. coli form dimers, are catalytically active, and their electrophoretic mobilities are similar to those of appropriate Clarkia PGIs. The nucleotide sequence of a gene encoding a plastid isozyme of C. unguiculata is described.     

Detection of genetic variants affecting cattle behaviour and their impact on milk production: a genome‐wide association study

Behaviour traits of cattle have been reported to affect important production traits, such as meat quality and milk performance as well as reproduction and health. Genetic predisposition is, together with environmental stimuli, undoubtedly involved in the development of behaviour phenotypes. Underlying molecular mechanisms affecting behaviour in general and behaviour and productions traits in particular still have to be studied in detail. Therefore, we performed a genome‐wide association study in an F₂ Charolais × German Holstein cross‐breed population to identify genetic variants that affect behaviour‐related traits assessed in an open‐field and novel‐object test and analysed their putative impact on milk performance. Of 37 201 tested single nucleotide polymorphism (SNPs), four showed a genome‐wide and 37 a chromosome‐wide significant association with behaviour traits assessed in both tests. Nine of the SNPs that were associated with behaviour traits likewise showed a nominal significant association with milk performance traits. On chromosomes 14 and 29, six SNPs were identified to be associated with exploratory behaviour and inactivity during the novel‐object test as well as with milk yield traits. Least squares means for behaviour and milk performance traits for these SNPs revealed that genotypes associated with higher inactivity and less exploratory behaviour promote higher milk yields. Whether these results are due to molecular mechanisms simultaneously affecting behaviour and milk performance or due to a behaviour predisposition, which causes indirect effects on milk performance by influencing individual reactivity, needs further investigation.     

Improved microdialysis technique.

A simple, inexpensive method is described for dialysis of microliter amounts of aqueous samples against large volumes of solution with complete recovery of the fluid dialyzed. An example is given of application of the method to separation of [³H]inulin from a monosaccharide.     

Denaturation thermodynamics of chicken cardiac metmyoglobin

The unfolding at pH 8 of chicken cardiac aquometmyoglobin was examined as a function of temperature and concentration of guanidinium chloride using the two-state model. The isothermal unfolding data at 25°C were fitted to Tanford's transfer model and the binding model of Aune and Tanford. The estimates obtained for ΔG_D) were virtually identical, viz., 8.3 ±0.3 kcal mol^?1. The chicken metmyoglobin is thus some 5.3 kcal mol^?1 less stable than that of sperm whale metmyoglobin. The unfolding parameters α and Δn were decreased 20% from those of mammalian myoglobins thus far examined, suggesting nonidentity of native conformations. The apparent enthalpy change on unfolding was dependent on both temperature and denaturant concentration. The decreases in the isothermal unfolding parameters from those of sperm whale are principally assigned to three of the 46 sequence changes.