Bellés-Sancho Paula, Golaz Daphné, Paszti Sarah, Vitale Alessandra, Liu Yilei, Bailly Aurélien, Eberl Leo, James Euan K, Pessi Gabriella
Department of Plant and Microbial Biology, University of Zurich, Zurich, Switzerland.
Laboratoires d'analyses médicales, Clinique de La Source, Lausanne, Switzerland.
Commun Biol. 2024 Dec 27;7(1):1706. doi: 10.1038/s42003-024-07385-x.
The beta-rhizobial strain Paraburkholderia phymatum STM815 is noteworthy for its wide host range in nodulating legumes, primarily mimosoids (over 50 different species) but also some papilionoids. It cannot, however, nodulate soybean (Glycine max [L.] Merr.), one of the world's most important crops. Here, we constructed a highly saturated genome-wide transposon library of a P. phymatum strain and employed a transposon sequencing (Tn-seq) approach to investigate the underlying genetic mechanisms of symbiotic incompatibility between P. phymatum and soybean. Soybean seedlings inoculated with the P. phymatum Tn-seq library display nodules on the roots that are mainly occupied by different mutants in a gene, nodS, coding for a methyltransferase involved in the biosynthesis of nodulation factors. The construction of a nodS deletion strain and a complemented mutant confirms that nodS is responsible for the nodulation-incompatibility of P. phymatum with soybean. Moreover, infection tests with different host plants reveal that NodS is necessary for optimal nodulation of common bean (Phaseolus vulgaris), but it is not required for nodulation of its natural host Mimosa pudica. In conclusion, our results suggest that NodS is involved in determining nodulation specificity of P. phymatum.
β-根瘤菌菌株费氏中华根瘤菌（Paraburkholderia phymatum）STM815因其在豆科植物结瘤方面广泛的宿主范围而值得关注，主要是含羞草类植物（超过50个不同物种），但也包括一些蝶形花科植物。然而，它不能使世界上最重要的作物之一大豆（Glycine max [L.] Merr.）结瘤。在此，我们构建了费氏中华根瘤菌菌株的一个高度饱和的全基因组转座子文库，并采用转座子测序（Tn-seq）方法来研究费氏中华根瘤菌与大豆之间共生不相容性的潜在遗传机制。用费氏中华根瘤菌Tn-seq文库接种的大豆幼苗在根上形成根瘤，这些根瘤主要被一个基因nodS中的不同突变体占据，该基因编码一种参与结瘤因子生物合成的甲基转移酶。nodS缺失菌株和互补突变体的构建证实，nodS导致了费氏中华根瘤菌与大豆的结瘤不相容性。此外，对不同宿主植物的感染试验表明，NodS对于菜豆（Phaseolus vulgaris）的最佳结瘤是必需的，但对于其天然宿主含羞草（Mimosa pudica）的结瘤则不是必需的。总之，我们的结果表明，NodS参与决定费氏中华根瘤菌的结瘤特异性。
