Fungal endophytes limit pathogen damage in a tropical tree
Fungal endophytes limit pathogen damage in a tropical tree
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DOI：
10.1073/pnas.2533483100
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发表时间：
2003-12-23
影响因子：
11.1
通讯作者：
Herre, EA
中科院分区：
文献类型：
--
作者：
Arnold, AE;Mejía, LC;Herre, EA
迄今为止，每种植物的无症状气生组织中都含有内生真菌，因此内生真菌是陆生植物群落中普遍存在但神秘的组成部分。与木本被子植物的叶子相关的真菌内生菌特别多样，然而，它们与宿主相互作用的基本方面是未知的。与垂直传播的相对物种贫乏的内生菌相比，木本被子植物的多样性，水平传播的内生菌被认为对宿主防御的贡献不大。在这里，我们记录高多样性，空间结构，和主机之间的亲和力与热带树木（可可，锦葵科）在低地巴拿马的叶内生菌。然后，我们表明，接种内生菌的无叶片与内生菌分离，经常从自然感染，无症状的主机显着降低叶片坏死和叶片死亡率时，T。可可幼苗受到主要病原体（疫霉菌）的挑战。与真菌接种诱导系统防御的报道相反，我们发现保护主要定位于内生菌感染的组织。此外，内生菌介导的保护是更大的成熟叶片，其中承担对真菌病原体比年轻的叶子更少的内在防御。在体外研究表明，主机的亲和力介导的叶化学，和保护可能介导的直接相互作用的内生菌与叶面病原体。总之，这些数据表明，木本被子植物的多样性，水平传播的内生菌的能力发挥重要的，但以前不受重视的作用，在主机防御。
Every plant species examined to date harbors endophytic fungi within its asymptomatic aerial tissues, such that endophytes represent a ubiquitous, yet cryptic, component of terrestrial plant communities. Fungal endophytes associated with leaves of woody angiosperms are especially diverse; yet, fundamental aspects of their interactions with hosts are unknown. In contrast to the relatively species-poor endophytes that are vertically transmitted and act as defensive mutualists of some temperate grasses, the diverse, horizontally transmitted endophytes of woody angiosperms are thought to contribute little to host defense. Here, we document high diversity, spatial structure, and host affinity among foliar endophytes associated with a tropical tree (Theobroma cacao, Malvaceae) across lowland Panama. We then show that inoculation of endophyte-free leaves with endophytes isolated frequently from naturally infected, asymptomatic hosts significantly decreases both leaf necrosis and leaf mortality when T. cacao seedlings are challenged with a major pathogen (Phytophthora sp.). In contrast to reports of fungal inoculation inducing systemic defense, we found that protection was primarily localized to endophyte-infected tissues. Further, endophyte-mediated protection was greater in mature leaves, which bear less intrinsic defense against fungal pathogens than do young leaves. In vitro studies suggest that host affinity is mediated by leaf chemistry, and that protection may be mediated by direct interactions of endophytes with foliar pathogens. Together, these data demonstrate the capacity of diverse, horizontally transmitted endophytes of woody angiosperms to play an important but previously unappreciated role in host defense.