1 Faculty of Agriculture, Tottori University, Tottori, Japan.
2 Functional Genomics Facility, NIBB Core Research Facilities, National Institute for Basic Biology, Okazaki, Japan.
Mol Plant Microbe Interact. 2018 Oct;31(10):1032-1047. doi: 10.1094/MPMI-01-18-0029-R. Epub 2018 Aug 22.
Achlorophylous and early developmental stages of chorolophylous orchids are highly dependent on carbon and other nutrients provided by mycorrhizal fungi, in a nutritional mode termed mycoheterotrophy. Previous findings have implied that some common properties at least partially underlie the mycorrhizal symbioses of mycoheterotrophic orchids and that of autotrophic arbuscular mycorrhizal (AM) plants; however, information about the molecular mechanisms of the relationship between orchids and their mycorrhizal fungi is limited. In this study, we characterized the molecular basis of an orchid-mycorrhizal (OM) symbiosis by analyzing the transcriptome of Bletilla striata at an early developmental stage associated with the mycorrhizal fungus Tulasnella sp. The essential components required for the establishment of mutual symbioses with AM fungi or rhizobia in most terrestrial plants were identified from the B. striata gene set. A cross-species gene complementation analysis showed one of the component genes, calcium and calmodulin-dependent protein kinase gene CCaMK in B. striata, retains functional characteristics of that in AM plants. The expression analysis revealed the activation of homologs of AM-related genes during the OM symbiosis. Our results suggest that orchids possess, at least partly, the molecular mechanisms common to AM plants.
缺乏叶绿素的早期发育阶段的兰花高度依赖于菌根真菌提供的碳和其他营养物质，这种营养模式被称为菌根异养。先前的研究结果表明，至少有一些共同的特性部分构成了菌根异养兰花和自主共生丛枝菌根（AM）植物的菌根共生关系；然而，关于兰花与其菌根真菌之间关系的分子机制的信息是有限的。在这项研究中，我们通过分析与菌根真菌 Tulasnella sp 相关的早期发育阶段的白芨转录组，来描述兰花-菌根（OM）共生的分子基础。从白芨基因组中鉴定出与 AM 真菌或根瘤菌在大多数陆生植物中建立相互共生所需的基本成分。种间基因互补分析表明，白芨中钙和钙调素依赖性蛋白激酶基因 CCaMK 的一个组成部分基因保留了 AM 植物中该基因的功能特征。表达分析显示，在 OM 共生过程中，AM 相关基因的同源物被激活。我们的研究结果表明，兰花至少部分具有与 AM 植物共同的分子机制。
