Involvement Of Ca²⁺·CaM Signaling In Resistance Response Of Wheat To Its Leaf Rust Disease

The regulatory effects of Ca²⁺,CaM signaling and the isoform specificity of CaM on the resistance response of wheat to its leaf rust disease were investigated by biochem-phamaceutical and molecular approach using the wheat isogeneic line and the suitable Puccinia triticica as materials. The results were as followings:1. The activities of peroxidase (POD) and phenylalanine ammonialyase (PAL) in the detached wheat leaves were increased 44.09% and 17.89%, respectively, by the pretreatment of seed of TcLr15 with 20 mmol/L CaCl₂ at 48h after the detached leaves were inoculated with virulent race 05-22-64â‘ , if compared to that of without Ca²⁺ pretreatment. No difference in the activities of polyphenoloxidase (PPO) and catalase (CAT) was found between treatment and untreatment.2. The activities of POD, PAL, PPO and CAT in the detached wheat leaves were all inhibited by the pretreatment of the seed of TcLr15 with CaM antagonists trifluoperazine (TFP), chlorpromazine (CPZ) and [(N-(6-aminohexyl)-5-chloro-1-naphathalene sulfonamide)] (W-7) after the detached leaves were inoculated with avirulent race 05-5-127â‘¢.3. The induction of POD activity in the detached wheat leaves by the avirulent race was delayed by pretreatment with three kinds of CaM antagonists tested in this study and the activity of POD was lower than the control during the incubation period. At 120 h after inoculation, the POD activities were decreased by 35.09%, 29.69%, and 41.79, respectively, by the pretreatment with TFP, CPZ and W-7 if compared that of control, while the PAL activities were decreased by 26.01% , 21.98% and 19.03%. At 48 h after inoculation, PPO activities in the detached wheat leaves were decreased by 9.42%,8.44% and 12.18% by TFP , CPZ and W-7 respectively if compared to that of without TFP , CPZ and W-7 pretreatment. The CAT activities of detached wheat leaves pretreated with TFP and CPZ were decrease by 22.04% and 30.22% and 23.2%, respectively, at 72 h after inoculation when compared to the control.4. The level of CaM and four CaM isoforms gene expression in wheat TcLr15 was tested by real-time Fluorescent Quantitative PCR (real-time PCR) after inoculation with virulent race and avirulent race respectively. No significant difference in the gene expression of CaM and its four isoforms was observed between the detached wheat leaves inoculated with virulent and without until 12 h after inoculation. The gene expression of CaM SF-1 in wheat at 48 h, 72 h and 96 h after inoculation with avirulent race 05-5-127â‘¢were increased by 24.6% , 26.6% and 38.8% compared with that of inoculation with virulent race 05-22-64â‘ . The gene expression of CaM SF-4 at 24 h, 48 h after inoculation with avirulent race 05-5-127â‘¢were increased by 26.8% and 28.0% if compared to that of inoculation with virulent race 05-22-64â‘ . The gene expression of CaM SF -2 in the incompatible interaction was lower than that of compatible interaction control from 24 h to 96 h after inoculation. No obvious difference in gene expression level of CaM SF-3 between compatible and incompatible interaction was found.5. The gene expression of CaM in wheat after inoculation with avirulent race 05-5-127â‘¢at the 24 h and 48 h were increased by 18.1% and 47.9% if compared to that of inoculation with virulent race 05-22-64â‘ , however, the gene expressive quantity of CaM in wheat at 72 h and 96 h after inoculation with avirulent race 05-5-127â‘¢is lower than that of inoculation with virulent race 05-22-64â‘ .Taken together, these data implied that Ca²⁺·CaM signaling might be involved in the regulation on wheat resistance against its leaf rust disease. More over, there exist a CaM isoform specificity for the involving in wheat defense against the infection of Puccinia triticina. The CaM SF-1 and CaM SF-4 genes may be related to wheat against the infection of Puccinia triticina. The CaM SF-2 may be related to wheat susceptible to the infection of Puccinia triticina. The CaM SF-3gene may be not related to wheat against the infection of Puccinia triticina.