Weber Roland W S, Stenger Eva, Meffert Anja, Hahn Matthias
Lehrbereich Biotechnologie, Universität Kaiserslautern, Paul-Ehrlich-Str. 23, D-67663 Kaiserslautern, Germany.
Mycol Res. 2004 Jun;108(Pt 6):662-71. doi: 10.1017/s0953756204000243.
Phoma medicaginis was isolated as the dominant endophyte from surface-sterilized shoots of Medicago sativa and M. lupulina growing outdoors. Plants were either symptomless or showed signs of infection in the shape of limited lesions which sometimes contained melanized pycnidial initials. Rapid colonization of host tissue and sporulation were observed within 9 d on dead plant material upon incubation in a moist chamber. Such colonized material, but not freshly harvested living tissue, contained brefeldin A (1.7 microg g(-1) D.W.). This toxin was also produced in pure culture (20 mg l(-1)) and in artificially inoculated autoclaved M. sativa stems (3 mg g(-1) D.W. =920 microg ml(-1)). The latter concentration of brefeldin A should be similar to that produced within a fruiting lesion of P. medicaginis and suppressed spore germination and growth of nine of 11 common phylloplane fungi tested. This metabolite may thus have a function in substrate defence after the switch from the endophytic to the saprotrophic period in the life-cycle of P. medicaginis following the death of infected host tissue.
从户外种植的紫花苜蓿和天蓝苜蓿经表面消毒的茎中分离出了首蓿茎点霉作为优势内生菌。这些植物要么无症状，要么表现出感染迹象，即出现有限的病斑，有时病斑中含有黑化的分生孢子器原基。在潮湿环境中培养9天内，在死亡的植物材料上观察到宿主组织的快速定殖和产孢。这种定殖的材料，而不是新鲜收获的活组织，含有布雷菲德菌素A（1.7微克/克干重）。这种毒素也在纯培养物（20毫克/升）和人工接种的经高压灭菌的紫花苜蓿茎中产生（3毫克/克干重=920微克/毫升）。布雷菲德菌素A的后一浓度应与首蓿茎点霉产孢病斑中产生的浓度相似，并且抑制了所测试的11种常见叶表真菌中的9种的孢子萌发和生长。因此，这种代谢产物可能在感染的宿主组织死亡后，在首蓿茎点霉生命周期中从内生阶段转变为腐生阶段后具有底物防御功能。
