The Research Of CaM Function In Defensive Reaction Of Corn Stimulated By HT-Toxin From Exserohilum Turcicum

The Northern Leaf Blight of Corn is one of the important leaf diseases of corn in the world. HT-toxin, which produced by Exserohilum turcicum, is not only a major toxigenic factor but also the elicitor to stimulate the defensive reaction of corn. To study the toxin will help to understand the moleculer of mechanism defensive reaction of plant.The change of CaM content in corn plants with different Ht gene, which were treated by HT-toxins from different turcicum races, had been studied. The experiment results showed that the CaM content in corn increased quickly at early 2~6 hours then decreased gradually after several hours in 14 compatible combinations and 14 controls treatments. But there was second ascending peak after the first ascending peak in incompatible combinations.There were different type lesions on corn leaves treated by HT-toxins in vitro through the acupuncture-wound bioassay: S type (susceptible) lesion-large and dark-green on compatible leaves but R type (resistant) lesion-small and yellow on incompatible leaves. This difference may be due to the defensive system could be stimulated or some substances could be produced which restrict the toxin's spreading and lead to small lesion spot in incompatible plant but not in compatible plant. The R type disease spot could act as a symbol of resistant reaction. The interesting thing is that the R lesion type would turn into S type while incompatible leaves treated by toxin after exposing to Trifluoperazine (TFP, one of the depressor of CaM). This suggested that TFP could hinder the resistant reaction, in other word, CaM played aimportant role in signal transduction of resistant reaction.Ca2+-CaM was one of the major resistant signal transductions in plant, which typical character was CaM content in plant could go up evidently after being stimulated and activated downriver resistant reaction, the depressor of CaM could inhibit the activity of CaM specificity and restrain or delay defensive reaction. In the interactions between com plants with different Ht-gene and HT-toxins from different turcicum races, CaM' quick changing and action of CaM depressor shared similar character. It was conclusion that the CaM was related to the plant defensive reaction.