Genetics, Faculty of Biology, Ludwig Maximilians University Munich, Germany.
Botany, Faculty of Biology, Ludwig Maximilians University Munich, Germany.
J Exp Bot. 2019 Mar 27;70(6):1903-1913. doi: 10.1093/jxb/erz057.
Lotus species develop infection threads to guide rhizobia into nodule cells. However, there is evidence that some species have a genetic repertoire to allow other modes of infection. By conducting confocal and electron microscopy, quantification of marker gene expression, and phenotypic analysis of transgenic roots infected with mutant rhizobia, we elucidated the infection mechanism used by Rhizobium leguminosarum Norway to colonize Lotus burttii. Rhizobium leguminosarum Norway induces a distinct host transcriptional response compared with Mesorhizobium loti. It infects L. burttii utilizing an epidermal and transcellular infection thread-independent mechanism at high frequency. The entry into plant cells occurs directly from the apoplast and is primarily mediated by 'peg'-like structures, the formation of which is dependent on the production of Nod factor by the rhizobia. These results demonstrate that Lotus species can exhibit duality in their infection mechanisms depending on the rhizobial strain that they encounter. This is especially relevant in the context of interactions in the rhizosphere where legumes do not encounter single strains, but complex rhizobial communities. Additionally, our findings support a perception mechanism at the nodule cell entry interface, reinforcing the idea that there are successive checkpoints during rhizobial infection.
莲属植物会形成侵染线来引导根瘤菌进入根瘤细胞。然而，有证据表明，某些莲属植物具有遗传潜能，可以采用其他侵染模式。通过共聚焦和电子显微镜、标记基因表达的定量分析以及转染突变根瘤菌的根的表型分析，我们阐明了根瘤菌挪威亚种侵染 Lotus burttii 的侵染机制。与 Mesorhizobium loti 相比，根瘤菌挪威亚种会诱导 Lotus burttii 产生明显不同的宿主转录反应。它可以高频利用表皮和穿细胞侵染线非依赖机制来侵染 Lotus burttii。细胞的侵入直接来自质外体，主要由“钉状”结构介导，其形成依赖于根瘤菌产生的结瘤因子。这些结果表明，莲属植物的侵染机制可能具有双重性，具体取决于其遇到的根瘤菌菌株。在根际相互作用的背景下，这一点尤为重要，因为豆类植物不会遇到单一菌株，而是会遇到复杂的根瘤菌群落。此外，我们的研究结果支持在根瘤细胞进入界面处存在感知机制，这进一步证实了在根瘤菌侵染过程中有连续的检查点。
