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Dernière mise à jour : Mai 2018

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Ten new plant genomes shed light on the evolution of nitrogen-fixing symbiosis

Ten new plant genomes shed light on the evolution of nitrogen-fixing symbiosis
Several researchers from the Plant Science Research Laboratory (LRSV - UMR 5546 CNRS / UPS), a constitutive unit of the TULIP LabEx, and 12 other institutions, published an article in the Science journal in May 2018. By comparing 37 plant genomes including 10 newly sequenced, they reveal the fragility of the nitrogen fixing symbiosis.

The root nodule symbiosis of plants with nitrogen-fixing bacteria impacts global nitrogen cycles and food production but is restricted to a subset of genera within a single clade of flowering plants. To explore the genetic basis for this scattered occurrence, the authors sequenced the genomes of ten plant species covering the diversity of nodule morphotypes, bacterial symbionts and infection strategies. In a genome-wide comparative analysis of a total of 37 plant species, they discovered signatures of multiple independent loss-of-function events in the indispensable symbiotic regulator NODULE INCEPTION (NIN) in ten out of 13 genomes of non-nodulating species within this clade.

Evolution of nitrogen fixing symbiosis

The nitrogen fixing symbiosis is present in some Fabales, Fagales, Cucurbitales and Rosales species. The distribution of this symbiosis may be the result of a gain in the ancestor common to these species followed by multiple losses or multiple gains. The second hypothesis was favored until today. Ten new genomes were sequenced and compared to 27 other genomes. Species that do not form symbiosis have genomic signatures indicating the loss of this symbiosis, thus validating the occurrence of multiple losses during evolution.

The discovery that multiple independent losses shaped the present day distribution of nitrogen-fixing root nodule symbiosis in plants reveals a phylogenetically wider distribution in evolutionary history and a so far underestimated selection pressure against this symbiosis.

See also

M. Griesmann, Y. Chang, X. Liu, Y. Song, G. Haberer, M. B. Crook, B. Billault-Penneteau, D. Lauressergues, J. Keller, L. Imanishi, Y. P. Roswanjaya, W. Kohlen, P. Pujic, K. Battenberg, N. Alloisio, Y. Liang, H. Hilhorst, M. G. Salgado, V. Hocher, H. Gherbi, S. Svistoonoff, J. J. Doyle, S. He, Y. Xu, S. Xu, J. Qu, Q. Gao, X. Fang, Y. Fu, P. Normand, A. M. Berry, L. G. Wall, J-M. Ané, K. Pawlowski, X. Xu, H. Yang, M. Spannagl, K. F. X. Mayer, G. K. Wong, M. Parniske, P.-M. Delaux, S. Cheng (2018) Phylogenomics reveals multiple losses of nitrogen-fixing root nodule symbiosis.Science. PMID:29794220. DOI:10.1126/science.aat1743