Search

Cold acclimation of winter wheat (Triticum aestivum L.) seedlings induces accumulation in the apoplast of taTLPs that are similar to thaumatin-like proteins (TLPs), which are pathogenesis-related proteins. We characterized a cDNA of WAS-3a encoding the major isoform of taTLPs from winter wheat cells and showed that WAS-3a transcripts were markedly increased by treatment with ABA and by treatment with elicitors (chitosan, β -glucan and cell wall fractions of Fusarium oxysporum and Microdochium nivale ) in wheat cells. To analyse the function of WAS-3a, a highly efficient expression system using wheat cells was established, and a large amount of recombinant WAS-3a protein (rWAS-3a) was obtained with near homogeneity. Antifungal assays using various fungi grown on agar plates revealed that rWAS-3a inhibits hyphal growth of pink snow mould, Microdochium nivale , at a low temperature. The results suggest that cold-induced taTLPs that accumulate in the apoplast contribute to snow mould resistance of winter wheat. [ABSTRACT FROM AUTHOR]

The LT50 values and soluble carbohydrate levels in wheat (Triticum aestivum L.) crowns and leaves were monitored throughout autumn and winter in cultivars varying in freezing tolerance and snow mold resistance during 1993/1994 and 1994/1995 in the field at Sapporo, Japan. During the first stage of hardening, from sowing to mid-November, the pattern of accumulation of mono- and disaccharides was similar for all cultivars. During the second stage of cold hardening, from mid-November to mid-December, the greatest accumulation of mono- and disaccharides, without a corresponding increase in fructan, was observed among the freezing-tolerant cultivars; and levels of simple saccharides rapidly decreased under snow cover. Conversely, levels of mono- and disaccharides in snow mold-resistant cultivars were less than 70% of those in freezing-tolerant cultivars before snow cover and maintained low levels throughout winter, while polysaccharide levels in snow mold-resistant cultivars were about 120% of those in freezing-tolerant cultivars in December. Sugar metabolism during the winter was examined using 18 cultivars in 1994/1995. LT50 values were correlated to the greatest extent with total mono- and disaccharide and fructan content among wheat cultivars excluding snow mold-resistant cultivars in December. Snow mold-resistant cultivars tended to metabolize carbohydrates more slowly until the end of the snow cover period. This result suggested that the enzymatic metabolism of the synthesis of sugars and the conversion of fructan to cryoprotective sugars in response to low temperatures, especially subzero ones, might be different between the two contrasting types in resistance to winter stress. [ABSTRACT FROM AUTHOR]