GFI is an abundant yeast DNA-binding protein, capable of binding to both ARS sequences and to the upstream regions of a number of nuclear genes coding for mitochondrial proteins (Dorsman et al., Nucl. Acids Res., 16 [1988] 7287-7301). GFI binding sites conform to the consensus RTCRYN5ACG, an element also present in the binding sites of factors designated SUF and TAF. These factors act as trans-activators of the constitutive transcription of the genes for ribosomal proteins S33 and L3 respectively. We now present evidence that GFI, TAF and SUF are probably the same protein. We speculate that one of the functions of GFI is the adjustment of the expression of a number of gene families to cell growth rate.

Photo. Arctic tundra peat in front of Stuphallet, Brøggerhalvøya, not far from Ny Alesund.Nutrient enrichment by nesting seabirds at the steep rocks of Stuphallet stimulates growth of many arctic plants. Because of the permafrost at 15 -20 cm below ground level, and soil melt-water in the summer period, the wet tundra soil is waterlogged. A peat profile was sampled with a depth of 105 cm using a motor-driven soil corer with a saw-tooth end. Photograph by J. Rozema. AbstractAs a reference for ongoing studies reconstructing past vegetation, climate and environment, pollen spectra in tundra peat profiles from Svalbard, were investigated. The base of tundra peat cores collected from Ny Å lesund, Stuphallet, Blomstrand and Isdammen has been 14 C dated to 350 -490 BP, 5710 BP, 4670 BP and 700 -900 BP, respectively. The Stuphallet and Blomstrand (Brøggerhalvøya) peat profiles were composed of a peat developed in a nutrient enriched and wet tundra environment of steep birdcliffs. Pollen concentrations were low, Brassicaceae pollen dominated the whole profile. In contrast, the Ny Å lesund and Isdammen profiles contained high pollen concentrations and suggest a nutrient-poor, dry tundra environment. Pollen of the polar willow, Salix polaris, occurred commonly throughout all four peat profiles. In the relatively high resolution (10 years per peat core sample) analysis of the Ny Å lesund core, starting before or at the beginning of the Little Ice Age (LIA, 16th-mid 19th century), dominance of Saxifraga oppositifolia indicates a cold and dry climate, followed by a decline of Saxifraga oppositifolia and gradual increase of Salix polaris after the LIA, which indicates a moist and milder climate.

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The response of tundra plants to enhanced UV-B radiation simulating 15 and 30% ozone depletion was studied at two high arctic sites (Isdammen and Adventdalen, 78°N, Svalbard).The set-up of the UV-B supplementation systems is described, consisting of large and small UV lamp arrays, installed in 1996 and 2002. After 7 years of exposure to enhanced UV-B radiation, plant cover, density, morphological (leaf fresh and dry weight, leaf thickness, leaf area, reproductive and ecophysiological parameters leaf UV-B absorbance, leaf phenolic content, leaf water content) were not affected by enhanced UV-B radiation. DNA damage in the leaves was not increased with enhanced UV-B in Salix polaris and Cassiope tetragona. DNA damage in Salix polaris leaves was higher than in leaves of C. tetragona. The length of male gametophyte moss plants of Polytrichum hyperboreum was reduced with elevated UV-B as well as the number of Pedicularis hirsuta plants per plot, but the inflorescence length of Bistorta vivipara was not significantly affected. We discuss the possible causes of tolerance of tundra plants to UV-B (absence of response to enhanced UV-B) in terms of methodology (supplementation versus exclusion), ecophysiological adaptations to UV-B and the biogeographical history of polar plants

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