1.11.83
EXPRESSION OF GENES IN WINTER WHEAT AFFECTED BY COLD ACCLIMATIONAND SNOW MOULD INFECTION

A ERGON l , SS KLEMSDAL l , DA GAUDET 2, A LAROCHE 2, T NAKAJIMA 3 and AM TRONSMO l
l Norwegian Crop Research Institute, Plant Protection Centre, Fellesbygget, N-1432 As, Norway; 2 Research Station, Agriculture and Agri-Food Canada, P.O.Box 3000, Main, Lethbridge, Alberta, Canada T1J 4B1; 3 Tohoku National Agricultural Experiment Station, Shimo-kuriyagawa, Morioka, 020-01 Japan

Background and objectives
Genes encoding defence related proteins are induced not only by pathogens, but also by various abiotic stresses[l]. Cold acclamation induces resistance to snow moulds[21]as well as to other pathogens. We have investigated whether cold acclimation-induced resistance could he due to a higher expression of defence-related genes. We have also isolated and partly characterized cold inducible winter wheat genes using the differential display technique.


Results and conclusions
Genes encoding the defence-related proteins chitinase, b-1,3-glucanase, peroxidase and PR--1a were induced in winter wheat by pink snow mould(Microdochium nivaie) and cottony snow mould (a Low Temperature Basidiomycete), as well as by abiotic factors during cold acclamation and incubation. Cold acclamation prior to inoculation facilitated the snow mould induced expression. The mechanism of this conditioning is not known, but the phenomenon may be of importance in cold acclimation-induced disease resistance and may have similarities with systemic aquired resistance. Acclimated plants of the snow mould resistant winter wheat line C114106 had a stronger expression of PR-1 a and a faster expression of chitinase and b-1,3-glucanase than the susceptible variety Norstar. Expression of defence--related genes was much lower at -3oC (the optimum temperature for cottony snow mould infection) than at 0oC. This indicates that this fungus may be restricted by defence-related proteins, avoiding them by being able to infect at -3oC. 3'-ends of cold induced mRNAs in etiolated winter wheat seedlings were isolated. One of these had 69-84% similarity on a nucleic acid basis with a family of cold induced genes in barley (BLT14), rye (RLT1412) and wheat. Two other cold induced mRNAs were also induced by M.nivaie infection.


References
1. Stintzi A, Heitz T, Prasad V, Wiedemann-Merdinoglu S, Kaufman S, Geoffroy P, Legrand M, Fritig B. 1993. Biochimie 75, 687-706. 2. Gaudet DA. 1994. Can. J. Plant Pathol. 16, 241-246.