Suetsugu Kenji, Okada Hidehito
Department of Biology, Graduate School of Science, Kobe University, Kobe, Hyogo, 657-8501, Japan.
Environ Microbiol. 2021 Oct;23(10):6328-6343. doi: 10.1111/1462-2920.15781.
Plants producing dust seeds often meet their carbon demands by exploiting fungi at the seedling stage. This germination strategy (i.e. mycoheterotrophic germination) has been investigated among orchidaceous and ericaceous plants exploiting Ascomycota or Basidiomycota. Although several other angiosperm lineages have evolved fully mycoheterotrophic relationships with Glomeromycota, the fungal identities involved in mycoheterotrophic germination remain largely unknown. Here, we conducted in situ seed baiting and high-throughput DNA barcoding to identify mycobionts associated with seedlings of Burmannia championii (Burmanniaceae: Dioscoreales) and Sciaphila megastyla (Triuridaceae: Pandanales), which have independently evolved full mycoheterotrophy. Subsequently, we revealed that both seedlings and adults in B. championii and S. megastyla predominantly associate with Glomeraceae. However, mycorrhizal communities are somewhat distinct between seedling and adult stages, particularly in S. megastyla. Notably, the dissimilarity of mycorrhizal communities between S. megastyla adult samples and S. megastyla seedling samples is significantly higher than that between B. championi adult samples and S. megastyla adult samples, based on some indices. This pattern is possibly due to both mycorrhizal shifts during ontogenetic development and convergent recruitment of cheating-susceptible fungi. The extensive fungal overlap in two unrelated mycoheterotrophic plants indicates that both species convergently exploit specific AM fungal phylotypes.
产生粉尘状种子的植物通常在幼苗阶段通过利用真菌来满足其碳需求。这种萌发策略（即菌根异养萌发）已在利用子囊菌门或担子菌门的兰科和杜鹃花科植物中得到研究。尽管其他几个被子植物谱系已经与球囊菌门进化出完全的菌根异养关系，但参与菌根异养萌发的真菌种类在很大程度上仍然未知。在这里，我们进行了原位种子诱捕和高通量DNA条形码分析，以鉴定与无叶莲（无叶莲科：薯蓣目）和大柱霉草（霉草科：露兜树目）幼苗相关的菌根共生体，这两种植物已独立进化出完全的菌根异养。随后，我们发现无叶莲和大柱霉草的幼苗和成年植株主要与球囊霉科相关。然而，菌根群落在幼苗和成年阶段有所不同，特别是在大柱霉草中。值得注意的是，基于一些指标，大柱霉草成年样本和大柱霉草幼苗样本之间的菌根群落差异显著高于无叶莲成年样本和大柱霉草成年样本之间的差异。这种模式可能是由于个体发育过程中的菌根转变以及对易作弊真菌的趋同招募。两种不相关的菌根异养植物中广泛的真菌重叠表明，这两个物种趋同地利用特定的丛枝菌根真菌系统型。
