Abstract：
During arbuscular mycorrhizal (AM) symbiosis, plant innate immunity is modulated to a prime state to allow for fungal colonization. The underlying mechanisms remain to be further explored. In this study, two rice genes encoding LysM extracellular (LysMe) proteins were investigated. By obtaining OsLysMepro:GUS transgenic plants and generating oslysme1, oslysme2 and oslysme1oslysme2 mutants via CRISPR/Cas9 technique, OsLysMe genes were revealed to be specifically induced in the arbusculated cells and mutations in either gene caused significantly reduced root colonization rate by AM fungus Rhizophagus irregularis. Overexpression of OsLysMe1 or OsLysMe2 dramatically increased the colonization rates in rice and Medicago truncatula. The electrophoretic mobility shift assay and dual-luciferase reporter assay supported that OsLysMe genes are regulated by OsWRI5a. Either OsLysMe1 or OsLysMe2 can efficiently rescue the impaired AM phenotype of the mtlysme2 mutant, supporting a conserved function of LysMe across monocotyledonous and dicotyledonous plants. The co-localization of OsLysMe proteins with the apoplast marker SP-OsRAmy3A implies their probable localization to the periarbuscular space (PAS) during symbiosis. Relative to the fungal biomass marker RiTEF, some defense-related genes showed disproportionately high expression levels in the oslysme mutants. These data support that rice plants deploy two OsLysMe proteins to facilitate AM symbiosis, likely by diminishing plant defense responses.
摘要：
在丛枝菌根（AM）共生过程中，植物先天性免疫被调节到原始状态以允许真菌定植。潜在机制仍有待进一步探索。在这项研究中,研究了编码LysM细胞外（LysMe）蛋白的两个水稻基因。通过获得OsLysMepro：GUS转基因植物，并通过CRISPR/Cas9技术产生oslysme1，oslysme2和oslysme1oslysme2突变体，OsLysMe基因被发现在成束的细胞中被特异性诱导，并且任一基因的突变均导致AM真菌RhizophagusRhizophicaris的根定植率显着降低。OsLysMe1或OsLysMe2的过表达显着提高了水稻和苜蓿的定殖率。电泳迁移率变化分析和双荧光素酶报告基因分析支持OsLysMe基因受OsWRI5a调控。OsLysMe1或OsLysMe2可以有效地挽救mtlysme2突变体受损的AM表型，支持LysMe在单子叶和双子叶植物中的保守功能。OsLysMe蛋白与质外体标记SP-OsRAmy3A的共定位暗示了它们在共生过程中可能定位到丛枝周围空间（PAS）。相对于真菌生物量标记物RiTEF，一些与防御相关的基因在oslysme突变体中显示出不成比例的高表达水平。这些数据支持水稻植物部署两种OsLysMe蛋白来促进AM共生，可能是通过减少植物防御反应。
