The determinants of specificity from Mycosphaerella species

利用豌豆疫病分枝杆菌系统研究了植物寄主-寄主特异性的机制。用高分子量激发子对豌豆组织产生两种类型的抗性。其中一个是鱼素的产生，另一个是感染抑制剂的形成。诱导后6 h内，损伤组织内的鱼素合成途径被激活，导致鱼素积累。处理后3 h内可诱导通路调节酶之一苯丙氨酸解氨酶（PAL）活化，1 h内检测PAL-和查尔酮合成酶基因的表达。同时存在的低分子量抑制因子被分泌到pinoides孢子萌发液中，导致这些防御反应延迟至少3小时。另一种抑制pinoides渗透的物质在处理后1-2小时后在未受伤组织的激发剂溶液中被检测到。其他真菌激发子也在处理组织中诱导了相同类型的排斥反应。这种类型的耐药也被抑制因子与激发因子的同时存在所否定。一些非致病性真菌能够在抑菌剂处理过的豌豆组织上产生这些感染。对豌豆无毒的真菌不能产生对豌豆植株有效的抑菌剂。因此，pinoides的抑制因子可能是确定豌豆植物- pinoides分枝杆菌系统特异性的原因。舌状分枝杆菌和m。梅洛尼还产生特异性决定因子，可抑制激发子诱导的各自寄主植物的防御反应。这些含糖和多肽物质的提纯工作正在进行中。

The mechanism of plant host-parasite specificity was investigated with a system of Mycosphaerella blight of pea. Two types of resistance were induced in pea tissues by the treatment with the high molecular weight elicitor prepared from the spore germination fluid of M. pinodes. One of them was pisatin production, and the other was the formation of infection inhibitors. Pisatin accumulation was caused by the activation of pisatin synthetic pathway in wounded tissues within 6 h after the eliciter-treatment. The activation of phenylalanine ammonia-lyase(PAL), one of regulatory enzymes in the pathway, was induced within 3 h, and the expressions of PAL- and chalcone synthase-gene were detected within 1 h after the treatment. The concomitant presence of the low molecular weight suppressor, which was secreated into spore germination fluid of M. pinodes, resulted in delay of these defense reactions for at least 3 h. Another substance which inhibits the penetration of M. pinodes was detected in the elicitor solution placed on uninjured tissues 1-2 h after the treatment. Other fungal elicitors also induced the same type of rejection reaction in the treated tissues. This type of resistance was also negated by the concomitant presence of suppressor with elicitor. Some nonpathogenic fungi of pea were able to establish these infection on the suppressor-treated tissues. The tested fungi avirulent to pea were not able to produce the suppressor effective to pea plant. The suppressor of M. pinodes, therefore, seems to be responsible for the determination of specificity in pea plant-Mycosphaerella pinodes system.Mycosphaerella ligulicola and My. melonis also produce the determinants of specificity which may negate the defense reaction of respective host plant induced by elicitor. The purification of these substances containing sugar and peptide is under way.