Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
Ecology Center, Utah State University, Logan, UT, USA.
ISME J. 2014 Feb;8(2):284-94. doi: 10.1038/ismej.2013.154. Epub 2013 Sep 12.
Arbuscular mycorrhizal fungi (AMF) are among the most abundant symbionts of plants, improving plant productivity and diversity. They are thought to mostly grow vegetatively, a trait assumed to limit adaptability. However, AMF can also harbor genetically different nuclei (nucleotypes). It has been shown that one AMF can produce genotypically novel offspring with proportions of different nucleotypes. We hypothesized that (1) AMF respond rapidly to a change of environment (plant host) through changes in the frequency of nucleotypes; (2) genotypically novel offspring exhibit different genetic responses to environmental change than the parent; and (3) genotypically novel offspring exhibit a wide range of phenotypic plasticity to a change of environment. We subjected AMF parents and offspring to a host shift. We observed rapid and large genotypic changes in all AMF lines that were not random. Genotypic and phenotypic responses were different among offspring and their parents. Even though growing vegetatively, AMF offspring display a broad range of genotypic and phenotypic changes in response to host shift. We conclude that AMF have the ability to rapidly produce variable progeny, increasing their probability to produce offspring with different fitness than their parents and, consequently, their potential adaptability to new environmental conditions. Such genotypic and phenotypic flexibility could be a fast alternative to sexual reproduction and is likely to be a key to the ecological success of AMF.
丛枝菌根真菌（AMF）是植物中最丰富的共生体之一，能够提高植物的生产力和多样性。它们被认为主要以营养生长的方式生长，这种特性被认为限制了它们的适应性。然而，AMF 也可以携带具有不同核型（基因型）的遗传物质。已经表明，一种 AMF 可以产生具有不同核型比例的具有基因型新颖的后代。我们假设：（1）AMF 通过核型频率的变化对环境（植物宿主）的变化迅速做出反应；（2）基因型新颖的后代对环境变化表现出与亲本不同的遗传响应；（3）基因型新颖的后代对环境变化表现出广泛的表型可塑性。我们使 AMF 亲本和后代经历了宿主转变。我们观察到所有 AMF 系的快速且大规模的基因型变化，这些变化不是随机的。后代及其亲本之间的基因型和表型响应不同。即使以营养生长的方式生长，AMF 后代也会对宿主转移表现出广泛的基因型和表型变化。我们得出结论，AMF 具有快速产生可变后代的能力，从而增加了它们产生比亲本具有不同适应性的后代的可能性，从而增加了它们对新环境条件的潜在适应性。这种基因型和表型的灵活性可能是有性繁殖的快速替代方式，并且很可能是 AMF 生态成功的关键。
