Pseudogenization of the rhizobium-responsive EXOPOLYSACCHARIDE RECEPTOR in Parasponia is a rare event in nodulating plants

作者：Simon Dupin, Joel D. Klein, Luuk Rutten, Rik Huisman, René Geurts · 发表于：BMC Plant Biology · 年份：2022 · DOI：10.1186/s12870-022-03606-9 · 被引用次数：8 · 研究领域：Legume Nitrogen Fixing Symbiosis、Metalloenzymes and iron-sulfur proteins、Plant Micronutrient Interactions and Effects

BACKGROUND: Nodule symbiosis with diazotrophic Frankia or rhizobium occurs in plant species belonging to ten taxonomic lineages within the related orders Fabales, Fagales, Cucurbitales, and Rosales. Phylogenomic studies indicate that this nitrogen-fixing nodulation trait has a single evolutionary origin. In legume model plants, the molecular interaction between plant and rhizobium microsymbiont is mapped to a significant degree. A specific LysM-type receptor kinase, LjEPR3 in Lotus japonicus and MtLYK10 in Medicago truncatula, was found to act in a secondary identity-based mechanism, controlling intracellular rhizobium infection. Furthermore, LjEPR3 showed to bind surface exopolysaccharides of Mesorhizobium loti, the diazotrophic microsymbiont of L. japonicus. EPR3 orthologous genes are not unique to legumes. Surprisingly, however, its ortholog EXOPOLYSACCHARIDE RECEPTOR (EPR) is pseudogenized in Parasponia, the only lineage of non-legume plants that nodulate also with rhizobium. RESULTS: Analysis of genome sequences showed that EPR3 orthologous genes are highly conserved in nodulating plants. We identified a conserved retrotransposon insertion in the EPR promoter region in three Parasponia species, which associates with defected transcriptional regulation of this gene. Subsequently, we studied the EPR gene of two Trema species as they represent the sister genus of Parasponia for which it is assumed it lost the nitrogen-fixing nodulation trait. Both Trema species possess appa...