Centre d'Ecologie Fonctionnelle et Evolutive (CNRS, UMR 5175), Equipe Interactions Biotiques, Montpellier, France.
Plant Signal Behav. 2010 Apr;5(4):349-53. doi: 10.4161/psb.5.4.10791. Epub 2010 Apr 25.
Mycoheterotrophic plants are achlorophyllous plants that obtain carbon from their mycorrhizal fungi. They are usually considered to associate with fungi that are (1) specific of each mycoheterotrophic species and (2) mycorrhizal on surrounding green plants, which are the ultimate carbon source of the entire system. Here we review recent works revealing that some mycoheterotrophic plants are not fungal-specific, and that some mycoheterotrophic orchids associate with saprophytic fungi. A re-examination of earlier data suggests that lower specificity may be less rare than supposed in mycoheterotrophic plants. Association between mycoheterotrophic orchids and saprophytic fungi arose several times in the evolution of the two partners. We speculate that this indirectly illustrates why transition from saprotrophy to mycorrhizal status is common in fungal evolution. Moreover, some unexpected fungi occasionally encountered in plant roots should not be discounted as 'molecular scraps', since these facultatively biotrophic encounters may evolve into mycorrhizal symbionts in some other plants.
菌异养植物是一种不含叶绿素的植物，它们从菌根真菌中获取碳。通常认为，它们与（1）每种菌异养物种特有的真菌和（2）周围绿色植物上的菌根真菌有关，而这些绿色植物是整个系统的最终碳源。在这里，我们回顾了最近的一些研究工作，这些工作揭示了一些菌异养植物并不是真菌特异性的，并且一些菌异养兰花与腐生真菌有关。对早期数据的重新检查表明，在菌异养植物中，较低的特异性可能并不像人们想象的那么罕见。菌异养兰花和腐生真菌之间的联系在这两个伙伴的进化中出现了几次。我们推测，这间接说明了为什么真菌进化中从腐生到菌根状态的转变如此普遍。此外，在植物根系中偶尔遇到的一些意想不到的真菌不应被视为“分子碎片”，因为在其他一些植物中，这些兼性生物营养的接触可能会进化为菌根共生体。
