To isolate chitinases and f8-1,3-glucanases from the intercellular space of oats (Avena sativa L.), primary leaves were infiltrated with buffer and subjected to gentle centrifugation to obtain intercellular washing fluid (IWF). Approximately 5% of the chitinase and 10% of the ,B-1,3-glucanase activity of the whole leaf were released. Only small amounts (0.01-0.03%) of the intracellular marker malate-dehydrogenase were released into the IWF during infiltration. Activities of chitinase and fl-1,3-glucanase in the IWF and in the leaf extract were compared by different chromatographic methods. On Sephadex G-75, chitinase appeared as a single peak (M, 29.8 kD) both in IWF and homogenate. ,-1,3-Glucanase, however, showed two peaks in the IWF (M, 52 and 31.3 kD), whereas the elution pattern of the homogenate showed only one major peak at 22 kD. Chromatofocusing indicated that the IWF contained four chitinases and five 68-1,3-glucanases. The elution pattern of the homogenate and IWF were similar with regard to the elution pH, but the peak intensities were distinctly different. Our results demonstrate that extracellular 0-1,3-glucanases are different from those located intracellularly. Extracellular and intracellular chitinases do not differ in molecular properties, except for one isozyme which seems to be confined to the extracellular space. We suggest that both enzymes might play a special role in pathogenesis during fungal infection.
The role of extracellular fl-1,3-glucanases and chitinases was investigated in oat leaves after infection with different rust fungi . The oat leaves (Avena sativa L .) were inoculated with the compatible rust Puccinia coronata f. sp . avenae and the two nonpathogens Puccinia recondita f. sp . tritici and Puccinia graminis f. sp. tritici . No alterations in enzyme activities were found in the compatible interaction . In the nonhost interaction with P. recondita ff sp . tritici (1-1,3-glucanase and chitinase activities increased by 100 % 24 h after infection. With P . graminis f. sp . tritici the activities of both enzymes increased about twofold after 48 h . In both nonhost interactions the observed increase in activity was due to the induction of an acidic fl-1,3-glucanase and a chitinase whereas the activity of the basic enzymes did not change . This increase is small compared to other systems and apparently the enzymes are not able to inhibit growth of the different rust fungi . Treatment of noninfected plants with the abiotic stress factor mercuric chloride induced necrosis and production of avenalumins but had no effect on the activities of the two enzymes investigated . In the nonhost systems no alteration of peroxidase activity and no induction of avenalumins could be found . Our results indicate that mechanisms other than the stress responses of oat plants studied so far are active in nonhost resistance .
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