LIPME, Université de Toulouse, INRAE, CNRS, Castanet-Tolosan 31326, France.
Rice Research Institute, Key Laboratory of Application and Safety Control of Genetically Modified Crops, Academy of Agricultural Sciences, Southwest University, Chongqing 400715, China.
Plant Cell Physiol. 2024 Jul 30;65(7):1149-1159. doi: 10.1093/pcp/pcae035.
Establishment of arbuscular mycorrhiza relies on a plant signaling pathway that can be activated by fungal chitinic signals such as short-chain chitooligosaccharides and lipo-chitooligosaccharides (LCOs). The tomato LysM receptor-like kinase SlLYK10 has high affinity for LCOs and is involved in root colonization by arbuscular mycorrhizal fungi (AMF); however, its role in LCO responses has not yet been studied. Here, we show that SlLYK10 proteins produced by the Sllyk10-1 and Sllyk10-2 mutant alleles, which both cause decreases in AMF colonization and carry mutations in LysM1 and 2, respectively, have similar LCO-binding affinities compared to the WT SlLYK10. However, the mutant forms were no longer able to induce cell death in Nicotiana benthamiana when co-expressed with MtLYK3, a Medicago truncatula LCO co-receptor, while they physically interacted with MtLYK3 in co-purification experiments. This suggests that the LysM mutations affect the ability of SlLYK10 to trigger signaling through a potential co-receptor rather than its ability to bind LCOs. Interestingly, tomato lines that contain a calcium (Ca2+) concentration reporter [genetically encoded Ca2+ indicators (GECO)], showed Ca2+ spiking in response to LCO applications, but this occurred only in inner cell layers of the roots, while short-chain chitooligosaccharides also induced Ca2+ spiking in the epidermis. Moreover, LCO-induced Ca2+ spiking was decreased in Sllyk10-1*GECO plants, suggesting that the decrease in AMF colonization in Sllyk10-1 is due to abnormal LCO signaling.
丛枝菌根的建立依赖于一种植物信号通路,该通路可以被真菌几丁质信号激活,如短链几丁寡糖和脂几丁寡糖(LCOs)。番茄 LysM 受体样激酶 SlLYK10 对 LCOs 具有高亲和力,并且参与丛枝菌根真菌(AMF)的根定殖;然而,其在 LCO 响应中的作用尚未被研究。在这里,我们表明 Sllyk10-1 和 Sllyk10-2 突变等位基因产生的 SlLYK10 蛋白,分别导致 AMF 定殖减少,并且分别在 LysM1 和 2 中发生突变,与 WT SlLYK10 相比,具有相似的 LCO 结合亲和力。然而,当与 Medicago truncatula LCO 共受体 MtLYK3 共表达时,突变形式不再能够诱导 Nicotiana benthamiana 细胞死亡,而在共纯化实验中它们与 MtLYK3 物理相互作用。这表明 LysM 突变影响 SlLYK10 通过潜在共受体触发信号的能力,而不是其结合 LCO 的能力。有趣的是,含有钙(Ca2+)浓度报告基因 [遗传编码 Ca2+ 指示剂(GECO)]的番茄系对 LCO 处理表现出 Ca2+ 爆发,但仅在根的内皮层中发生,而短链几丁寡糖也诱导表皮中的 Ca2+ 爆发。此外,Sllyk10-1*GECO 植物中 LCO 诱导的 Ca2+ 爆发减少,表明 Sllyk10-1 中 AMF 定殖减少是由于异常的 LCO 信号。