ISOLATION AND CHARACTERIZATION OF A BARLEY CHITINASE GENOMIC CLONE - EXPRESSION IN POWDERY MILDEW INFECTED BARLEY

Chitinases (E.C.3.2.1.14) are thought to play an important role in the defense of plants against fungal invasion. By screening a barley geno mic library with a previously identified chitinase cDNA clone (clone 1 0), a genomic clone was isolated and characterized by DNA sequencing o f the chitinase coding region and flanking sequences. This clone conta ins an open reading frame capable of coding for a 34 kD chitinase. Com parison of the amino acid sequence of the encoded protein with other b arley chitinases suggests that the genomic clone encodes chitinase T, which has been characterized extensively by protein sequencing. Treatm ent of barley leaves and aleurone protoplasts with N-acetyl glucosamin e oligomers which act as elicitors in other plants, did not lead to th e elevation of the levels of the chitinases. However, infection of bar ley seedlings with the powdery mildew fungus, Erysiphe graminis, resul ted in the induction of several isoforms of chitinase. The level and n umber of chitinase isozymes was correlated with the severity of infect ion. The infection-related chitinases found in barley leaves are diffe rent from those found in seeds.