Tominaga Takaya, Miura Chihiro, Sumigawa Yuuka, Hirose Yukine, Yamaguchi Katsushi, Shigenobu Shuji, Mine Akira, Kaminaka Hironori
The United Graduate School of Agricultural Sciences, Tottori University, Tottori, Japan.
Faculty of Agriculture, Tottori University, Tottori, Japan.
Front Plant Sci. 2021 Dec 16;12:795695. doi: 10.3389/fpls.2021.795695. eCollection 2021.
Morphotypes of arbuscular mycorrhizal (AM) symbiosis, , , and Intermediate types, are mainly determined by host plant lineages. It was reported that the phytohormone gibberellin (GA) inhibits the establishment of -type AM symbiosis in legume plants. In contrast, we previously reported that GA promotes the establishment of -type AM symbiosis in , while suppressing -type AM symbiosis in a legume model plant, . This raises a hitherto unexplored possibility that GA-mediated transcriptional reprogramming during AM symbiosis is different among plant lineages as the AM morphotypes are distinct. Here, our comparative transcriptomics revealed that several symbiosis-related genes were commonly upregulated upon AM fungal colonization in (-type), (Intermediate-type), and (-type). Despite of the similarities, the fungal colonization levels and the expression of symbiosis-related genes were suppressed in and but were promoted in in the presence of GA. Moreover, exogenous GA inhibited the expression of genes involved in biosynthetic process of the pre-symbiotic signal component, strigolactone, which resulted in the reduction of its endogenous accumulation in and . Additionally, differential regulation of genes involved in sugar metabolism suggested that disaccharides metabolized in AM roots would be different between and /. Therefore, this study uncovered the conserved transcriptional responses during mycorrhization regardless of the distinct AM morphotype. Meanwhile, we also found diverse responses to GA among phylogenetically distant AM host plants.
丛枝菌根（AM）共生的形态类型，即、和中间类型，主要由宿主植物谱系决定。据报道，植物激素赤霉素（GA）抑制豆科植物中 - 型AM共生的建立。相比之下，我们之前报道过GA促进中 - 型AM共生的建立，同时在豆科模式植物中抑制 - 型AM共生。这就提出了一种迄今为止尚未探索的可能性，即由于AM形态类型不同，AM共生过程中GA介导的转录重编程在不同植物谱系中存在差异。在这里，我们的比较转录组学研究表明，在（ - 型）、（中间型）和（ - 型）中，几种与共生相关的基因在AM真菌定殖后通常会上调。尽管存在相似性，但在GA存在的情况下，和中的真菌定殖水平以及共生相关基因的表达受到抑制，而在中则得到促进。此外，外源GA抑制了共生前信号成分独脚金内酯生物合成过程中相关基因的表达，导致其在和中的内源性积累减少。另外，糖代谢相关基因的差异调节表明，AM根中代谢的二糖在和/之间会有所不同。因此，本研究揭示了无论AM形态类型如何，菌根形成过程中保守的转录反应。同时，我们还发现了在系统发育距离较远的AM宿主植物中对GA的不同反应。
