疫霉蛋白激发子PB90对病原菌生长与致病力的影响

 激发子PB90是由棉疫病菌分泌的可诱发非寄主植物系统获得抗病性的一类新型蛋白激发子。本文就该激发子在棉疫病菌生长发育及致病过程中的作用进行了研究。采用胶体金标记发现该激发子主要分布在棉疫病菌的细胞壁上,该激发子可以分泌到细胞外;在离体条件下,PB90的多克隆抗体并不抑制棉疫病菌游动孢子的萌发和孢子萌发后形成菌落的能力,而且抗体包埋的游动孢子仍能激发非寄主植物烟草的过敏性坏死反应;但是,抗体的包埋处理可以使棉疫病菌的游动孢子丧失对棉花的致病力。结果表明,特异性存在于细胞壁上的疫霉蛋白激发子PB90是棉疫病菌的一种重要的毒性因子,在病菌对棉花的致病过程中具有重要作用;此外本研究结果还提示PB90并不是惟一能诱导非寄主烟草过敏性反应的棉疫病菌激发子,除了PB90之外,棉疫病菌还能产生其它的激发子诱导烟草的过敏性坏死反应。

Effect of the protein elicitor PB90 from Phytophthora boehmeriae on growth and virulence of the pathogen itself

The role of the protein elicitor PB90 in compatible interaction between P. boehmeriae and cotton was studied. The elicitor was previously shown to be an efficient elicitor of the hypersensitive reaction and an AVR factor conditioning nonhost resistance in Nicotiana tobacum. The treatment of P. boehmeriae zoospore with antiserum raised against the elicitor PB90 resulted in the loss of virulence activity on host cotton, indicating that the elicitor could contribute to virulence of P. boehmeriae on cotton (Fig.4). However, the hypersensitive reaction was also observed in nonhost tobacco leaf infiltrated with zoospore treated by different doses of antiserum (Fig.2). The antiserum did not inhibit zoospore germination and creation of effective single zoospore isolates in vitro (Table 1 &Fig.3). The antiserum allowed localization of PB90 by immunogold-labeling on the cell wall of the mycelium and encysting zoospores when the fungus was grown in vitro (Fig.2). The results provide strong evidence that PB90 has dual functions with promoting virulence on host cotton and functioning as avirulence factor by eliciting hypersensitive reaction and resistance in nonhost tobacco.