Strobel Gary
Department of Plant Sciences, Montana State University, Bozeman, MT 59717, USA.
J Fungi (Basel). 2018 May 16;4(2):57. doi: 10.3390/jof4020057.
As is true with animal species, plants also have an associated microflora including endophytes as well as microbes associated with the phyllosphere and rhizosphere (plant surfaces) and this is considered the plant microbiome. However, those organisms within virtually all tissues and organs of the plant are known as endophytes. Most often fungi are the most frequently recovered endophytes from plant tissues, but bacterial forms generally occur in greater numbers, but not in species varieties. The exact biological/biochemical role of the endophyte in the plant and how it interacts with the plant and other endophytes and plant associated organisms has not been intensely and carefully examined. However, this has not stopped investigators in exploring the direct utility of endophytes in boosting plant production, and discovering that endophytes can directly influence the plant to resist temperature extremes, drought, as well as the presence of disease causing organisms. Also, because of the relationships that endophytes seem to have with their host plants, they make a myriad of biologically active compounds some of which are classified as antibiotics, antioxidants, anticancer agents, volatile antimicrobial agents, immunosuppressive compounds, plant growth promoting agents, and insecticides. These endophytic compounds represent a wide range of organic molecules including terpenoids, peptides, carbohydrates, aromatics, hydrocarbons and others and it seems that these compounds may have a role in the host microbe relationship. Most recently and quite surprisingly, some endophytes have been discovered that make hydrocarbons of the types found in diesel and gasoline fuels. In addition, recently discovered are epigenetic factors relating to the biology and biochemistry of endophytes. Interestingly, only about 1⁻2% of the entire spectrum of 300,000 known plants have been studied for their endophyte composition. Additionally, only a few plants have ever been completely studied including all tissues for the microbes within them. Likewise, the vast majority of plants, including those in oceans and lower plant forms, have never been examined for their endophytes. Furthermore, endophytes representing the "microbiome" of world's major food plants as they exist in their native "centers of origin" are largely unknown. This non-classical review is intended to provide background information on aspects of developments in endophyte biology and more importantly the identification of new questions in this field that need to be addressed. The review is primarily based on the author's long held experience in this field.
与动物物种一样，植物也有一个相关的微生物群落，包括内生菌以及与叶际和根际（植物表面）相关的微生物，这被认为是植物微生物组。然而，几乎存在于植物所有组织和器官中的那些生物体被称为内生菌。最常从植物组织中分离出来的内生菌是真菌，但细菌形态通常数量更多，但种类不同。内生菌在植物中的具体生物学/生物化学作用以及它如何与植物、其他内生菌和与植物相关的生物体相互作用，尚未得到深入和仔细的研究。然而，这并没有阻止研究人员探索内生菌在提高植物产量方面的直接效用，并发现内生菌可以直接影响植物抵抗极端温度、干旱以及致病生物体的存在。此外，由于内生菌似乎与其宿主植物存在关系，它们会产生无数种生物活性化合物，其中一些被归类为抗生素、抗氧化剂、抗癌剂、挥发性抗菌剂、免疫抑制化合物、植物生长促进剂和杀虫剂。这些内生菌化合物代表了广泛的有机分子，包括萜类化合物、肽、碳水化合物、芳香族化合物、碳氢化合物等，而且这些化合物似乎在宿主与微生物的关系中发挥作用。最近且相当令人惊讶的是，发现了一些能产生柴油和汽油燃料中那种类型碳氢化合物的内生菌。此外，最近还发现了与内生菌生物学和生物化学相关的表观遗传因素。有趣的是，在已知的30万种植物中，只有约1% - 2%的植物被研究过其内生菌组成。此外，只有少数植物被全面研究过，包括其所有组织中的微生物。同样，绝大多数植物，包括海洋中的植物和低等植物形态，从未被检测过其内生菌。此外，作为世界主要粮食植物“原生起源中心”存在的内生菌，即其“微生物组”，在很大程度上是未知的。这篇非传统综述旨在提供内生菌生物学发展方面的背景信息，更重要的是识别该领域需要解决的新问题。这篇综述主要基于作者在该领域长期积累的经验。
