Department of Chemical and Biological Sciences, Japan Women's University, 2-8-1 Mejirodai, Bunkyo-ku, Tokyo 112-8681, Japan.
J Plant Res. 2013 Jan;126(1):41-50. doi: 10.1007/s10265-012-0511-9. Epub 2012 Jul 18.
Mycorrhizal symbiosis is common among land plants including pteridophytes (monilophytes and lycophytes). In pteridophytes with diplohaplontic life cycle, mycorrhizal formations were mostly reported for sporophytes, but very few for gametophytes. To clarify the mycorrhizal association of photosynthetic gametophytes, field-collected gametophytes of Angiopteris lygodiifolia (Marattiaceae, n = 52) and Osmunda japonica (Osmundaceae, n = 45) were examined using microscopic and molecular techniques. Collected gametophytes were mostly cut into two pieces. One piece was used for light and scanning microscopic observations, and the other for molecular identification of plant species (chloroplast rbcL sequences) and mycorrhizal fungi (small subunit rDNA sequences). Microscopic observations showed that 96 % (50/52) of Angiopteris and 95 % (41/43) of Osmunda gametophytes contained intracellular hyphae with arbuscules and/or vesicles and fungal colonization was limited to the inner tissue of the thick midribs (cushion). Fungal DNA analyses showed that 92 % (48/52) of Angiopteris and 92 % (35/38) of Osmunda have sequences of arbuscular mycorrhizal fungi, which were highly divergent but all belonged to Glomus group A. These results suggest that A. lygodiifolia and O. japonica gametophytes consistently form arbuscular mycorrhizae. Mycorrhizal formation in wild fern gametophytes, based on large-scale sampling with molecular identification of host plant species, was demonstrated for the first time.
菌根共生在包括蕨类植物（单叶植物和石松类植物）在内的陆地植物中很常见。在具有双单倍体生活史的蕨类植物中，菌根的形成大多发生在孢子体上，但在配子体上很少见。为了阐明光合作用配子体的菌根共生关系，我们使用显微镜和分子技术对采集到的凤尾蕨（凤尾蕨科，n=52）和日本紫萁（紫萁科，n=45）的配子体进行了研究。采集到的配子体大多被切成两块。一块用于光镜和扫描电镜观察，另一块用于植物物种（叶绿体 rbcL 序列）和菌根真菌（小亚基 rDNA 序列）的分子鉴定。显微镜观察表明，96%（52/52）的凤尾蕨和 95%（41/43）的日本紫萁配子体含有具丛枝和/或泡囊的细胞内菌丝，真菌定殖仅限于厚中肋（垫）的内部组织。真菌 DNA 分析表明，92%（48/52）的凤尾蕨和 92%（35/38）的日本紫萁具有丛枝菌根真菌的序列，这些序列高度分化，但都属于 Glomus 组 A。这些结果表明，凤尾蕨和日本紫萁的配子体始终形成丛枝菌根。首次基于宿主植物物种的大规模取样和分子鉴定，证明了野生蕨类配子体的菌根形成。
