MOLECULAR-SIZE AND NET CHARGE OF PATHOGENESIS-RELATED ENZYMES FROM BARLEY (HORDEUM-VULGARE L., V. CARAT) INFECTED WITH DRECHSLERA-TERES F TERES (SACCH.) SHOEM

Molecular size and net charge of isoforms of pathogenesis-related (PR) chitinase, beta-1,3-glucanase and peroxidase were studied in uninfect ed barley (Hordeum vulgare L., v. Karat) leaves and in barley leaves i nfected with the pathogenic fungus Drechslera teres f. teres (Sacch.) Shoem. Molecular characteristics were determined by time-dependent pol yacrylamide gradient gel electrophoresis under native conditions and b y applying an extended version of the computer program MOL-MASS (Rothe , G. M., Weidmann, H., Electrophoresis 1991, 12, 703-709). Uninfected barley leaves contained predominantly one peroxidase isozyme but also three very weak peroxidases. Activities of all of these three peroxida ses increased considerably after infection with Drechslera teres. The molecular masses of peroxidases 1 and 3 were estimated to be 38 +/- 5 and 42 +/- 7 kDa and their apparent valences at pH 8.4 were Z = 3.13 a nd 3.20, respectively. Amongst the chitinase isoforms, chitinase 1 and chitinase 2 appeared after infection, while chitinase 3 was also obse rved in uninfected leaves of barley. The molecular mass of chitinase 3 (31 +/- 6 kDa; f/f(o) = 1.20) was larger than that of chitinase 1 (20 +/- 2 kDa; f/f(o) = 1.04) and chitinase 2 (23 +/- 3 kDa; f/f(o) = 1.0 6). The valence of constitutive chitinase 3 (Z = 1.44 +/- 0.81) at pH 8.4 was lower than that of adaptive chitinase 1 (Z = 3.27 +/- 1.02) an d chi tinase 2 (Z = 2.96 +/- 1.38). Infection of barley leaves with Dr echslera teres also induced the hydrolytic enzyme beta-1,3-glucanase 1 ; beta-1,3-glucanase 2 appeared in uninfected and in infected leaves. Constitutive beta-1,3-glucanase 2 was smaller (molecular mass 19 +/- k Da; f/f(o) = 1.05) than adaptive beta-1,3-glucanase 1 (molecular mass 26 +/- 4 kDa; f/f(o) = 1.07). The valence of adaptive beta-1,3-glucana se 1 (Z = 9.58 +/- 4.17) was approximately threefold that of beta-1,3- glucanase 2 (Z = 2.80 +/- 0.93).