Laboratoire de Recherche en Sciences Végétales, Université de Toulouse, CNRS, UPS, 24 chemin de Borde Rouge, Auzeville, BP42617, 31326 Castanet Tolosan, France.
Laboratoire de Recherche en Sciences Végétales, Université de Toulouse, CNRS, UPS, 24 chemin de Borde Rouge, Auzeville, BP42617, 31326 Castanet Tolosan, France; Toulouse Tech Transfer, Maison de la Recherche et de la Valorisation, 118 route de Narbonne, 31432 Toulouse, France.
Cell Host Microbe. 2017 Jan 11;21(1):106-112. doi: 10.1016/j.chom.2016.12.001. Epub 2016 Dec 29.
Arbuscular mycorrhizal (AM) symbiosis associates most plants with fungi of the phylum Glomeromycota. The fungus penetrates into roots and forms within cortical cell branched structures called arbuscules for nutrient exchange. We discovered that miR171b has a mismatched cleavage site and is unable to downregulate the miR171 family target gene, LOM1 (LOST MERISTEMS 1). This mismatched cleavage site is conserved among plants that establish AM symbiosis, but not in non-mycotrophic plants. Unlike other members of the miR171 family, miR171b stimulates AM symbiosis and is expressed specifically in root cells that contain arbuscules. MiR171b protects LOM1 from negative regulation by other miR171 family members. These findings uncover a unique mechanism of positive post-transcriptional regulation of gene expression by miRNAs and demonstrate its relevance for the establishment of AM symbiosis.
丛枝菌根（AM）共生将大多数植物与球囊霉门的真菌联系在一起。真菌穿透根系并在皮层细胞内形成分支结构，称为丛枝，用于营养交换。我们发现 miR171b 具有不匹配的切割位点，无法下调 miR171 家族靶基因 LOM1（丧失分生组织 1）。这个不匹配的切割位点在建立 AM 共生的植物中是保守的，但在非菌根植物中则不是。与 miR171 家族的其他成员不同，miR171b 刺激 AM 共生，并特异性地在含有丛枝的根细胞中表达。miR171b 保护 LOM1 免受其他 miR171 家族成员的负调控。这些发现揭示了 miRNA 对基因表达进行正向转录后调控的独特机制，并证明了其与 AM 共生建立的相关性。
