Laboratoire de Biotechnologie Végétale, Université Libre de Bruxelles, 12 rue des Professeurs Jeener et Brachet, Gosselies, Belgium.
Environ Microbiol. 2011 May;13(5):1236-52. doi: 10.1111/j.1462-2920.2011.02424.x. Epub 2011 Feb 17.
The phytopathogenic Actinomycete Rhodococcus fascians induces leafy galls on a wide range of hosts, causing major economical losses in the ornamentals industry. Although differences in the responsivity occur within species, no plant tested so far could be considered resistant to R. fascians strain D188 infection. Here, we observed that members of the genus Dalbergia, which belong to the Fabaceae, did not develop leafy galls when challenged with R. fascians and we set out to unravel the mechanism of this recalcitrance. Whereas organic extracts of Dalbergia tissues exhibited toxicity towards the bacteria, more importantly, dichloromethane bark extracts inhibited the induction of bacterial virulence gene expression without any apparent loss of viability, illustrating that resistance is likely multifactorial. The virulence quencher was identified as a new prenylated isoflavanone, termed perbergin, and specifically targeted the AttR regulon (a LysR-type transcriptional regulator) which is imperative for the switch of R. fascians from an epiphytic to a pathogenic lifestyle. The mode of action of perbergin demonstrated that just like in Gram-negative host-microbe interactions, also in Gram-positive phytopathogens autoregulation is being targeted by the plant as an efficient means of defence. Moreover, the identification of perbergin opens the path to disease control in affected nurseries.
植物病原放线菌罗霍氏菌会在广泛的宿主上引起叶状瘿瘤，给观赏植物产业造成重大经济损失。尽管物种内存在反应差异，但迄今为止，没有一种植物被认为对罗霍氏菌 D188 菌株的感染具有抗性。在这里，我们观察到属于豆科的黄檀属成员在受到罗霍氏菌的攻击时不会产生叶状瘿瘤，我们开始揭示这种抗逆性的机制。虽然黄檀组织的有机提取物对细菌具有毒性，但更重要的是，二氯甲烷树皮提取物抑制了细菌毒力基因表达的诱导，而没有明显的活力丧失，这表明抗性可能是多因素的。这种杀菌物质被鉴定为一种新的类异戊二烯基异黄酮，称为柏醇，并特异性靶向 AttR 调控群（一种 LysR 型转录调节因子），这对于罗霍氏菌从附生状态到致病状态的转变至关重要。柏醇的作用模式表明，就像在革兰氏阴性宿主-微生物相互作用中一样，植物也将革兰氏阳性植物病原菌的自身调节作为一种有效的防御手段。此外，柏醇的鉴定为受影响苗圃的疾病控制开辟了道路。
