Fragmented environment affects birch leaf endophytes.

The effect of environmental fragmentation on the species distribution and frequency of horizontally transmitted endophytic fungi in Betula pubescens and Betula pendula leaves was studied in an archipelago in southwestern Finland. The study system consisted of 14 islands, ranging in size and distance to the mainland, and five mainland sites. Endophytic fungi were grown out from surface-sterilized leaves. The frequency of endophytic fungi mainly depended on the size of the island, explaining 32-35% of the variation, and the distance to the mainland explaining 29-35% of the variation. The birch trees on the largest islands near the mainland had the highest endophyte frequencies. Fusicladium betulae, Gnomonia setacea and Melanconium betulinum were the most commonly isolated fungi. Foliar endophytes of birch trees are able to disperse to fairly fragmented areas, but their frequencies seem to depend on environmental isolation and size of the island.

Genetic and environmental factors affecting the allergenicity of birch (Betula pubescens ssp. czerepanovii [Orl.] Hämet-ahti) pollen.

BACKGROUND: Environmental variation, such as an increase of mean temperature due to the greenhouse effect, as well as the genetic factors may affect the allergenicity of pollen and thus, the prevalence of allergies. The connection between these factors and the allergen content of pollen is poorly understood. OBJECTIVES: To evaluate the role of environmental and genetic factors on the allergenicity of birch pollen. METHODS: Mountain birch (Betula pubescens ssp. czerepanovii (Orl.) Hämet-Ahti) pollen was studied using SDS-PAGE and IgE-immunoblotting. Pollen samples were collected from the trees of 10 half-sib families. The study trees from each family were reared in two tree line gardens where the daily mean temperatures were different during the growing season. RESULTS: The quantitative analysis of band intensities suggested that the responses of the major birch pollen allergen, Bet v 1, were stronger in the samples collected from the garden with higher daily mean temperature. Half-sib families and individual trees differed in their Bet v 1 content. CONCLUSIONS: Our results show that both genetic and environmental factors have an effect on the amount of Bet v 1. This suggests that breeding for trees low in allergen content may be possible.

Effects of air pollution and other environmental factors on birch pollen allergens.

To determine the effects of anthropogenic pollution on water-soluble proteins and specifically allergens in birch (Betula pendula and B. pubescens) pollen, we analyzed extracts of pollen from the pollution gradient around a factory complex (emitting sulfur oxides and heavy metals) by sodium dodecyl sulfate (SDS)--polyacrylamide gel electrophoresis (PAGE) and IgE immunoblotting. In addition, tree density-associated shading of the tree habitat, and quantity and quality of proteins and allergens in pollen of the two birch species were studied. The two studied birch species gave identical allergen profiles even though their protein profiles differed. Distance from the factory did not affect the amount of birch pollen major allergen, Bet v 1 (17 kDa), or of two other strong allergens (23 and 36 kDa). Trees growing in shaded places had significantly stronger responses to Bet v 1 and to the 23-kDa allergen than trees growing in open or half-open environments. Thus, we propose that combined heavy metal and sulfur dioxide pollution does not have an important effect on birch pollen allergens. Instead, other factors, e.g., shading and soil properties of the tree habitat, as well as the genetic background of the tree, may have a stronger influence on the quantity and relative composition of allergens.