Arbuscular mycorrhizal fungi possess a CLAVATA3/Endosperm surrounding region‐ elated gene that positively regulates symbiosis

First author: Morgane Le Marquer; Affiliations: Huazhong Agricultural University (华中农业大学): Wuhan, China

Corresponding author: Nicolas Frei dit Frey

The arbuscular mycorrhizal (AM; 丛枝菌根) symbiosis (共生) is a beneficial association established between land plants and the members of a subphylum (亚门) of fungi, the Glomeromycotina (球囊菌亚门). How the two symbiotic partners regulate their association is still enigmatic (似谜的). Secreted fungal peptides are candidates for regulating this interaction. We searched for fungal peptides with similarities with known plant signaling peptides. We identified CLAVATA (CLV)/EMBRYO SURROUNDING REGION (ESR)‐RELATED PROTEIN (CLE) genes in phylogenetically distant AM fungi: four Rhizophagus (根内球囊霉属) species and one Gigaspora (巨孢囊霉属) species. These CLE genes encode a signal peptide for secretion and the conserved CLE C‐ erminal motif. They seem to be absent in the other fungal clades. R. irregularis and G. rosea CLE genes (RiCLE1 and GrCLE1) are transcriptionally induced in symbiotic versus asymbiotic conditions. Exogenous application of synthetic RiCLE1 peptide on Medicago truncatula affects root architecture, by slowing the apical growth of primary roots and stimulating the formation of lateral roots. In addition, pre‐ reatement of seedlings with RiCLE1 peptide stimulates mycorrhization (菌根化). Our findings demonstrate for the first time that in addition to plants and nematodes (线虫类), AM fungi also possess CLE genes. These results pave the way for deciphering (破译) new mechanisms by which AM fungi modulate plant cellular responses during the establishment of AM symbiosis.

丛枝菌根共生是陆地植物与真菌球囊菌亚门物种之间建立起的一种互利互惠关系。然而，共生的双方是如何调控他们这种关系的还有很多未知的地方。真菌分泌的多肽是调控共生关系的候选介质之一。作者比较了真菌分泌的多肽与植物信号肽之间的相似性，结果发现在四个进化上距离较远的真菌：3个根内球囊霉属物种和1个巨孢囊霉属物种中存在CLE基因。这些CLE基因编码一个能够分泌出去的信号肽，并且具有保守的CLE碳端继续。这些多肽似乎在其它的真菌中并不存在。相比于非共生条件下，R. irregularis和G. rosea的CLE基因，即RiCLE1和GrCLE1在共生条件下受到诱导转录。对苜蓿外施合成的RiCLE1多肽能够影响其根系结构，主要表现在主根的顶端生长被延缓，而侧根的形成受到了刺激。另外，对幼苗用RiCLE1多肽进行预处理能够有效的刺激菌根化。本文的发现第一次揭示了除了植物和某些线虫外，丛枝菌根真菌也能够产生CLE基因。本文的研究有助于我们进一步理解丛枝菌根真菌在共生过程中调节植物细胞响应的分子机制。

doi: https://doi.org/10.1111/nph.15643

Journal: New Phytologist

Published date: 16 December, 2018