Changed Activities Of Defense-Related Enzymes In Nicotiana-TMV Interaction Under High-temperature Stress

In this experiment,symptom masking of TMV-inoculated tobacco,ester isoenzyme activity,defense-related enzyme activity and Ca²⁺ signal under high-temperature stress were analyzed.The results were as followed:1.High-temperature stress can impact the consequence of tobacco-TMV interaction.TMV-inoculated plants had a postponed mosaic-emergeing,decreased symptom severity under high-temperature stress.When treated at 45℃, tobacco mosaic was 10 days later than control ,and the topper leaves became almost normal with decreased symptom severity.Tobacco plants treated at 45℃18h could grow normally.At 48℃24h,mosaic emerged 20 days later and plants grew well. The optimum stress for symptom masking was 48℃24h.2.Ester isoenzymes PAGE assay revealed that under high-temperature stress both TMV-inoculated plants and non-inoculated plants had similar ester isoenzyme profiles except certain band with difference in band density.The results suggested that high-temperature stress can not cause any genetic mutation,and the impact of high-temperature stress on TMV-tobacco interaction possibly be involved in the induction of host viral resistance.3.By activity analysis of defense-related enzymes,high-temperature stress was showed to be able to activate POD,PPO,PAL and SOD in TMV-inoculated plants. PAL activity increased 60.41% at 4 days post stress(dps),that of SOD did 2.58% at 6 dps,and that of POD and PPO at 8 dps increased 4.47,1.44-fold ,respectively.4.By application of Ca²⁺ prior to high temperature stress,POD and SOD activities were showed to increase significantly,but decrease by Ca²⁺ specific chelator EGTA and CaM specific inhibitors CPZ.However, there was a similar latent-period in the three cases.Importantly,mosaic symptom was slightly masked by treatment of Ca²⁺,but aggravated by treatment of EGTA and CPZ.These results above gave us a hint that Ca²⁺ as a signal possibly involved in high-temperature-induced symptom masking.