Mycorrhizal fungi supply nitrogen to host plants in Arctic tundra and boreal forests: 15N is the key signal.

Symbiotic fungi's role in providing nitrogen to host plants is well-studied in tundra at Toolik Lake, Alaska, but little-studied in the adjoining boreal forest ecosystem. Along a 570 km north-south transect from the Yukon River to the North Slope of Alaska, the 15N content was strongly reduced in ectomycorrhizal and ericoid mycorrhizal plants including Betula, Salix, Picea mariana (P. Mill.

A simple method for the preparation of single-stranded polydeoxynucleotides of desired length.

A method for the preparation of homogeneous, single-stranded polydeoxynucleotides of desired length up to 800 bases is described. The procedure entails 1) generation of double-stranded DNA of desired length by PCR using a pair of primers of which one is biotinylated and the other is either unlabeled or fluorescently labeled, 2) isolation of PCR products by agarose slab gel electrophoresis, 3) recovery of desired product by electroelution, 4) binding of the product to streptavidin-coated magnetic beads and is followed by 5) duplex denaturation and removal of the unbound single strand that is either unlabeled or fluorescently labeled. Final product characteristics were determined by capillary gel electrophoresis with fluorescence detection.

High speed automated DNA sequencing in ultrathin slab gels.

We have developed a high speed instrument for automated DNA sequence analysis. The apparatus employs laser excitation and a cooled CCD detector for the parallel detection of up to 18 sets of four fluorescently labeled DNA sequencing reactions during their electrophoretic separation in ultrathin (50-100 microns) denaturing polyacrylamide gels. Four hundred and fifty bases of sequence information is obtained from 100 ng of M13 template DNA in less than one hour, corresponding to an overall instrument throughput of over 8000 bases/hr.

High speed DNA sequencing by capillary electrophoresis.

A major challenge of the Human Genome Initiative is the development of a rapid, accurate, and efficient DNA sequencing technology. A major limitation of current technology is the relatively long time required to perform the gel electrophoretic separations of DNA fragments produced in the sequencing reactions. We demonstrate here that it is possible to increase the speed of sequence analysis by over an order of magnitude by performing the electrophoresis and detection in ultra thin capillary gels.

High-speed separations of DNA sequencing reactions by capillary electrophoresis.

Fluorescently labeled DNA fragments generated in enzymatic sequencing reactions are rapidly separated by capillary gel electrophoresis and detected at attomole levels within the gel-filled capillary. The application of this technology to automated DNA sequence analysis may permit the development of a second generation automated sequencer capable of efficient and cost-effective sequence analysis on the genomic scale.