Molecular analysis of two Ypt/Rab-related sequences isolated from soybean (Glycine max) DNA libraries

From nodule and seedling cDNA libraries we isolated cDNA copies of two mRNAs, derived from the genes gmrl and gmr2, encoding members of the Ypt/Rab family of small GTP-binding proteins. Two deduced protein products, GMR1 and GMR2, were found to be nearly identical differing by only four amino acids in the analysed parts. The two putative proteins are 79% identical to the previously described ARA small GTPase from Arabidopsis thaliana. The GMR proteins may thus be the counterpart of the ARA protein and may perform a related biological function in Glycine max. The gmr2 genomic sequence was isolated and structurally analysed. Expression analyses by northern and cDNA-based PCR showed that the gmr1 and gmr2 genes are constitutively expressed in different plant organs, although at a slightly higher level in callus culture. The classification of the gmr sequences as relatives of the Ypt/Rab family suggests that the deduced GMR proteins are involved in control of processes related to vesicle trafficking in plant cells.     

Trace metals in Swedish natural fresh waters

Water samples were collected from unpolluted waters in southern and northern Sweden to show the range of natural trace metal concentrations. The results do not indicate any significant differences in metal levels between the two study areas. Negative correlations with pH exist for total concentrations of Cd, Pb, Al, Mn and Zn. The dissolved (dialysable) metal fractions also increase with increasing acidity. The concentration of humic substances influences the distribution of Fe, Mn, Al, Pb, Cr, Co and As, as shown by positive correlations with water colour.Increasing alkalinity has a limiting effect upon concentrations and annual fluctuations of Cd and Pb, and to some extent on Zn, in running waters.     

Succession and fluctuation in the vegetation of a Dutch beach plain

The development of the vegetation of a brackish sand flat with scattered embryo-dunes on one of the West Frisian islands, Schiermonnikoog (The Netherlands), was recorded over a ten-year period. Some persisting trends, as well as pronounced annual fluctuations, were observed. Therophyte populations are especially vulnerable to environmental fluctuation. The behaviour of various species populations is discussed in relation to environmental instability and life-forms. Special attention is paid to the shuttling of populations of short-lived species on the dune slope. The zonation of the latter may vary, which could be ascribed to their reaction on abiotic conditions as affected by specific life-history characteristics, viz. the germination period, the duration of the life-cycle and the mode of reproduction. Some concluding remarks are made about succession and the role species of different life-forms play in this process.     

Avian scale development. VI. Ultrastructure of the keratinizing cells of reticulate scales

Reticulate scales develop as radial symmetrical anlagen, in contrast to scuttate scales which appear initially as “epidermal placodes.” Unlike scuttate scales whose outer and inner epidermal surfaces elaborate β-and α-type keratins, respectively, reticulate scales elaborate only one type of epidermal surface which has been reported to give an α-type, X-ray diffraction pattern. We find that, histologically and ultrastructurally, this surface differs from either epidermal surface of scuttate scales. The keratinizing cells become filled with long interweaving bundles of α-filaments which aggregate into rather homogeneous α-fibrils. Keratohyalin granules, which have been shown to be associated with other keratinizing regions in the bird, do not form during the keratinization of reticulate scale epidermis.