Department of Forest Sciences, University of Helsinki, PO Box 27, FIN-00014 Helsinki, Finland.
Tree Physiol. 2011 Apr;31(4):438-51. doi: 10.1093/treephys/tpr027.
The saprotrophic fungus Phlebiopsis gigantea has been used for several years as a biocontrol agent against the conifer pathogen Heterobasidion annosum. Although the effectiveness of P. gigantea in biocontrol has been shown empirically, the long-term effect on living conifer trees as well as the mechanism underlying its antagonistic activity is still unknown. An additional concern is the potential of P. gigantea to acquire a necrotrophic habit through adaptation to living wood tissues. By using a combination of histochemical, molecular and transcript profiling (454 sequencing), we investigated under in vitro conditions the necrotrophic capability of P. gigantea and induced localized resistance as a mechanism for its biocontrol action. Pinus sylvestris seedlings (10 years old) were challenged on the xylem surface with P. gigantea or H. annosum. Both fungi provoked strong necrotic lesions, but after prolonged incubation, P. gigantea lesions shrank and ceased to expand further. Tree seedlings pre-treated with P. gigantea further restricted H. annosum-induced necrosis and had more lignified cells. The 454 sequencing revealed elevated transcript levels of genes important for lignification, cell death regulation and jasmonic acid signalling. The results suggest that induced localized resistance is a contributory factor for the biocontrol efficacy of P. gigantea, and it has a limited necrotrophic capability compared with H. annosum.
腐生真菌 Phlebiopsis gigantea 多年来一直被用作针对针叶树病原菌 Heterobasidion annosum 的生物防治剂。尽管已经从经验上证明了 P. gigantea 在生物防治中的有效性，但它对活的针叶树的长期影响以及其拮抗活性的机制仍不清楚。另一个令人担忧的问题是，P. gigantea 通过适应活木组织可能获得坏死习性。通过结合组织化学、分子和转录谱（454 测序）分析，我们在体外条件下研究了 P. gigantea 的坏死能力以及其作为生物防治作用的机制所诱导的局部抗性。我们用 P. gigantea 或 H. annosum 对 10 年生的欧洲赤松幼苗的木质部表面进行了挑战。两种真菌都引起了强烈的坏死病变，但经过长时间的培养，P. gigantea 的病变缩小并停止进一步扩张。用 P. gigantea 预处理的树幼苗进一步限制了 H. annosum 诱导的坏死，并使更多的木质细胞木质化。454 测序显示，与木质化、细胞死亡调控和茉莉酸信号传导相关的重要基因的转录水平升高。结果表明，诱导的局部抗性是 P. gigantea 生物防治效果的一个贡献因素，与 H. annosum 相比，它的坏死能力有限。
