香蕉黑星病菌侵入前发育的Ca2+/CaM依赖信号研究

测定Phyllosticta musarum 在不同疏水性的人工表面上的孢子萌发率和附着胞形成率,以及Ca2+,CaM依赖信号系统是否参与了P.musarum侵入前阶段的发育调控.结果表明,P.musarum在侵染寄主时形成一种专门的附着胞作为侵染结构,刚性的疏水表面有利于诱导P musarum分生孢子的萌发.刚性表面则有利于附着胞的形成,而对这种与侵染相关的特化结构即附着胞的发育影响不显著.加入外源Ca2+,不论浓度如何都能促进分生孢子萌发,而附着胞形成率在高浓度外源Ca2+存在时则明显下降.Ca2+敖合剂EGTA有抑制孢子萌发和附着胞形成的作用,但在EGTA中加入Ca2+载体A23187和CaCl2可部分缓解EGTA的这种抑制作用.磷酸酯酶C(PLC)抑制剂Neomycin可以抑制附着胞形成.Ca2+通道阻断剂TMB-8和Nicaldipine,CaM拈抗剂Chloropromazine在微摩尔剂量水平上均可抑制附着胞形成.证明由Caz+/CaM信号系统控制的生化过程参与了P.musarum在寄主香蕉表面侵入前的形态建成.

Calcium/Calmodulin-Denpendent Signaling for Prepenetration Development in Phyllosticta musarum

Studies on the effects of calcium/calmodulin-dependent signaling on the conidial germination and appressorium formation of Phyllosticta musarum will help us understand the controlling mechanism for prepenetration development in P. musarum, and provide new target sites for development of effective control measures. Germination and appressorial formation on different artificial surfaces with different physicochemical characteristics were observed and determined. Five inhibitors were tested on conidial germination and appressorium formation to find if the calcium/calmodulin-dependent signaling system was involved in prepenetration morphogenesis in P. musarum pathogene on banana. P. musarum formed a specialized infection structure, an appressorium, for host infection. Hard hydrophobic surface induced spore germination. Hard surface induced appressorium formation in P. musarum, but did not have significant effect on the development of the infection-related appressorium. Exogenous Ca2+, regardless of its concentration, augmented conidial germination, but decreased appressorial differentiation at higher concentrations. Inhibition of appressorium formation by calcium chelator(EGTA)was partly restored by the addition of calcium ionophore A23187 or CaCl2. Phospholipase C inhibitor(Neomycin)could inhibit appressorium formation. Calcium modulators(TMB-8 and Nicardipine)and calmodulin antagonists(Chloropromazine)reduced appressorium formation at micro-molar levels. These results suggested that the biochemical processes controlled by the calcium/calmodulin signaling system were involved in the induction of prepenetration morphogenesis in P. musarum pathogen on banana host surface.