Elevation of extracellular β-1,3-glucanase and chitinase activities in rose in response to treatment with acibenzolar-S-methyl and infection by D. rosae

Changes in activities of β-1,3-glucanase and chitinase were determined in intercellular fluids of leaves of in vitro rose shoots at various times after treatment with acibenzolar-S-methyl (BTH, a benzothiadiazole derivative; trade name Bion 50WG) or inoculation with Diplocarpon rosae. The results indicate that BTH treatment led to enhanced activities of β-1,3-glucanase and chitinase in the intercellular spaces of rose leaves. An increase in extracellular β-1,3-glucanase and chitinase activities was also found in D. rosae-infected leaves. However, the increase in enzyme activities occurred much more rapidly and was more strongly enhanced in D. rosae-infected leaves that were previously treated with BTH, suggesting that the increased β-1,3-glucanase and chitinase may play a role in restricting the development of disease symptoms on the rose leaves infected with D. rosae. The expression patterns of rose β-1,3-glucanase and chitinase isoforms were investigated on native PAGE with specific staining techniques. A similar induction pattern of these enzymes was observed in both treatments. The increased β-1,3-glucanase and chitinase activities are mainly due to the enhanced expression of β-1,3-glucanase isoform G2 and chitinase isoforms C1 and C2. These isoforms are likely to be a part of rose defense responses to pathogen attack.