1. Fungal endophytes (FE) are an important component of leaf microbial communities. They usually live asymptomatically within leaf tissues; however, FE can provide additional defensive features against microbial pathogens to the host. Leaf functional traits (LFTs) regulate FE entry, colonization and community composition in plants.
2. There is evidence that thin leaves with less structural and chemical traits but high nutrient content are more prone to FE colonization than well-defended thick leaves. This illustrates the relevance of trade-offs (= an increase in a trait, with a decrease in another trait) in LFTs, suggesting that the leaf economics spectrum (LES, which describes relationships in a suite of leaf traits aligned from a resource-acquisitive to a resource-conservative ecological strategy) may be a predictor of FE colonization and community composition in plants.
3. We hypothesize that LES-modulated changes in the leaf internal environment (i.e. thin, low-defended vs. thick, well-defended leaves) will (a) have consequences for host resistance to pathogens due to changes in the FE colonization and diversity and, subsequently, in the foliar chemical profile and (b) may cause a switch in FE behaviour to a pathogenic lifestyle.
4. Synthesis. Still, our knowledge of how the coexistence between host plants and FE is regulated remains limited. LFTs may act as relevant ecological hub of FE colonization, community composition and life behaviour in natural ecosystems, with potential bottom-up effects on other organisms, including pathogens. We highlight and discuss critical aspects in this topic and end by proposing new avenues of research in this emerging field.

中文翻译：

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叶片功能性状在真菌内生菌定植中的作用：对宿主-病原体相互作用的潜在影响

1. 真菌内生菌 (FE) 是叶微生物群落的重要组成部分。它们通常无症状地生活在叶组织中；然而，FE 可以为宿主提供针对微生物病原体的额外防御功能。叶功能性状 (LFT) 调节植物中的 FE 进入、定植和群落组成。
2. 有证据表明，结构和化学特征较少但营养含量高的薄叶比防御良好的厚叶更容易发生 FE 定植。这说明了 LFT 中权衡（= 一个性状的增加，另一个性状的减少）的相关性，表明叶经济学谱（LES，它描述了与资源获取者对齐的一组叶性状中的关系）资源节约型生态策略）可能是植物中 FE 定植和群落组成的预测因子。
3. 我们假设叶片内部环境中 LES 调节的变化（即薄的、低防御的与厚的、防御良好的叶片）将 (a) 由于 FE 定植和多样性的变化而对宿主对病原体的抗性产生影响，并且，随后，在叶面化学特征中，（b）可能导致 FE 行为转变为致病性生活方式。
4. 合成。尽管如此，我们对寄主植物和 FE 之间如何共存的了解仍然有限。LFT 可能作为自然生态系统中 FE 定植、群落组成和生命行为的相关生态中心，对其他生物（包括病原体）具有潜在的自下而上的影响。我们强调并讨论了该主题的关键方面，并提出了这一新兴领域的新研究途径。