Peroxidases are known to locate in various cell compartments,
and this localization determines their functions.
Thus, ionically bound enzymes are involved in
the cell-wall strengthening [18]. Healthy plants of
resistant cultivar displayed a higher activity of ionically
bound peroxidase (Fig. 2d) in comparison with susceptible
one. Infection differently affected this peroxidase
form in different cultivars. Thus, in the seedlings of susceptible
cv. Zhnitsa, cell-wall peroxidase activity
increased and remained at the level exceeding that in
control plants during the entire experiment (Fig. 2b). In
the seedlings of resistant cv. Zarya, the activity of ionically
bound peroxidase was below the control level
(Fig. 2d). This might be related to enhanced processes
of lignification and, correspondingly, with a tighter
enzyme binding to the cell walls (Fig. 3). It was shown
that resistant wheat cultivars infected with pathogenic
fungi were characterized by earlier and more intense
lignin accumulation.An increase in peroxidase activity in response to
infection can occur due to the activation of presynthesized
enzyme molecules and to de novo enzyme synthesis
[13, 20]. The analysis of peroxidase isoenzyme patterns
in 48 h after infection revealed cultivar-specific
differences in both cytoplasmic and ionically-bound
with the cell walls enzymes (Fig. 4). In the seedlings of
the resistant cultivar, in the set of cytoplasmic peroxidases,
anionic peroxidases with pI ~ 3.5 and ~ 4.5
appeared and cationic peroxidases with pI ~ 9.8 (Fig. 4a,
lane 6) were activated; the latter were demonstrated
earlier to be able of binding to the phytopathogen cell
wall [21]. In addition, in resistant plants, anionic peroxidases
were activated in the fraction bound ionically
with the cell walls as well.