Data_Sheet_1_Tomato LysM Receptor-Like Kinase SlLYK12 Is Involved in Arbuscular Mycorrhizal Symbiosis.DOCX

Arbuscular mycorrhiza (AM) is a widespread symbiotic relationship between plants and fungi (Glomeromycota), which improves the supply of water and nutrients to host plants. AM symbiosis is set in motion by fungal chitooligosaccharides and lipochitooligosaccharides, which are perceived by plant-specific LysM-type receptor kinases (LYK). In rice this involves OsCERK1, a LYK also essential for chitin triggered innate immunity. In contrast in legumes, the CERK1 homologous gene experienced duplication events resulting in subfunctionalization. However, it remains unknown whether this subfunctionalization is legume-specific, or has occurred also in other dicot plant species. We identified four CERK1 homologs in tomato (SlLYK1, SlLYK11, SlLYK12, and SlLYK13) and investigated their roles in chitin signaling and AM symbiosis. We found that knockdown of SlLYK12 in tomato significantly reduced AM colonization, whereas chitin-induced responses were unaffected. In contrast, knockdown of SlLYK1 resulted in reduced responses to chitin, but did not alter responses to AM fungi. Moreover, ectopic overexpression of SlLYK1 and SlLYK13 in Nicotiana benthamiana induced cell death, whereas SlLYK12 overexpression did not. Based on our results and comparison with rice OsCERK1, we hypothesize that OsCERK1 orthologs in tomato underwent gene duplication, leading to the subfunctionalization of immunity and symbiosis.

丛枝菌根（Arbuscular mycorrhiza, AM）是一类广泛分布于植物与真菌（球囊菌门，Glomeromycota）之间的共生关系，可有效提升宿主植物的水分与养分供应能力。AM共生的启动由真菌分泌的几丁寡糖与脂几丁寡糖介导，二者可被植物特异性LysM型受体激酶（LysM-type receptor kinases，LYK）识别。在水稻中，该识别过程涉及OsCERK1——一种同样参与几丁质触发的先天免疫反应的LysM型受体激酶。与之相对，豆科植物中的CERK1同源基因经历了基因复制事件，进而产生亚功能化。目前尚不清楚这种亚功能化是否为豆科植物所特有，亦或在其他双子叶植物类群中同样存在。本研究在番茄中鉴定到4个CERK1同源基因（SlLYK1、SlLYK11、SlLYK12及SlLYK13），并探究了它们在几丁质信号转导与AM共生中的功能。实验结果显示，番茄中SlLYK12的基因敲低会显著降低AM的定殖水平，但几丁质诱导的免疫反应未受明显影响。与之相反，SlLYK1的基因敲低会削弱植物对几丁质的响应，但并未改变其对AM真菌的应答能力。此外，在本氏烟草（Nicotiana benthamiana）中异位过表达SlLYK1与SlLYK13可诱导细胞死亡，而过表达SlLYK12则无此现象。基于本研究结果并与水稻OsCERK1进行对比分析，我们提出如下假说：番茄中的OsCERK1直向同源基因经历了基因复制事件，最终导致免疫与共生通路发生亚功能化。