Ectopic expression of the GRAS-type transcriptional regulator in triggers contrasting effects on symbioses.

Introduction: Plants strictly control root endosymbioses with nutrient-scavenging arbuscular endomycorrhizal fungi or nodule inducing diazotrophic bacteria. The GRAS-type transcriptional regulator NODULATION SIGNALING PATHWAY 2 () is a conserved hub in this process. The -regulated transcriptional network is instrumental in balancing nutrient homeostasis with symbiotic interactions.

A rare non-canonical splice site in Trema orientalis SYMRK does not affect its dual symbiotic functioning in endomycorrhiza and rhizobium nodulation.

Background: Nitrogen-fixing nodules occur in ten related taxonomic lineages interspersed with lineages of non-nodulating plant species. Nodules result from an endosymbiosis between plants and diazotrophic bacteria; rhizobia in the case of legumes and Parasponia and Frankia in the case of actinorhizal species. Nodulating plants share a conserved set of symbiosis genes, whereas related non-nodulating sister species show pseudogenization of several key nodulation-specific genes.

Innovations in two genes kickstarted the evolution of nitrogen-fixing nodules.

The root nodule symbiosis between plants and nitrogen-fixing bacteria is a fascinating trait limited to several plant species. Given the agronomic potential of transferring this symbiosis to nonleguminous crops, the symbiosis has attracted researchers' attention for over a century. The origins of this symbiosis can be traced back to a single ancestor, around 110 million years ago.

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

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.

Synthetic bacterial community derived from a desert rhizosphere confers salt stress resilience to tomato in the presence of a soil microbiome.

The root bacterial microbiome is important for the general health of the plant. Additionally, it can enhance tolerance to abiotic stresses, exemplified by plant species found in extreme ecological niches like deserts. These complex microbe-plant interactions can be simplified by constructing synthetic bacterial communities or SynComs from the root microbiome.

High Salt Levels Reduced Dissimilarities in Root-Associated Microbiomes of Two Barley Genotypes.

Plants harbor in and at their roots bacterial microbiomes that contribute to their health and fitness. The microbiome composition is controlled by the environment and plant genotype. Previously, it was shown that the plant genotype-dependent dissimilarity of root microbiome composition of different species becomes smaller under drought stress.

The Effect of Exogenous Nitrate on LCO Signalling, Cytokinin Accumulation, and Nodule Initiation in .

Nitrogen fixation by rhizobia is a highly energy-demanding process. Therefore, nodule initiation in legumes is tightly regulated. Environmental nitrate is a potent inhibitor of nodulation.

The BOP-type co-transcriptional regulator NODULE ROOT1 promotes stem secondary growth of the tropical Cannabaceae tree Parasponia andersonii.

Tree stems undergo a massive secondary growth in which secondary xylem and phloem tissues arise from the vascular cambium. Vascular cambium activity is driven by endogenous developmental signalling cues and environmental stimuli. Current knowledge regarding the genetic regulation of cambium activity and secondary growth is still far from complete.

Phylogeographic distribution of rhizobia nodulating common bean (Phaseolus vulgaris L.) in Ethiopia.

Rhizobia are soilborne bacteria that form symbiotic relations with legumes and fix atmospheric nitrogen. The nitrogen fixation potential depends on several factors such as the type of host and symbionts and on environmental factors that affect the distribution of rhizobia. We isolated bacteria nodulating common bean in Southern Ethiopia to evaluate their genetic diversity and phylogeography at nucleotide, locus (gene/haplotype) and species levels of genetic hierarchy.

Duplication of Symbiotic Lysin Motif Receptors Predates the Evolution of Nitrogen-Fixing Nodule Symbiosis.

Rhizobium nitrogen-fixing nodule symbiosis occurs in two taxonomic lineages: legumes (Fabaceae) and the genus (Cannabaceae). Both symbioses are initiated upon the perception of rhizobium-secreted lipochitooligosaccharides (LCOs), called Nod factors. Studies in the model legumes and showed that rhizobium LCOs are perceived by a heteromeric receptor complex of distinct Lys motif (LysM)-type transmembrane receptors named NOD FACTOR RECEPTOR1 (LjNFR1) and LjNFR5 () and LYSM DOMAIN CONTAINING RECEPTOR KINASE3 (MtLYK3)-NOD FACTOR PERCEPTION (MtNFP; ).

A Homeotic Mutation Changes Legume Nodule Ontogeny into Actinorhizal-Type Ontogeny.

Some plants fix atmospheric nitrogen by hosting symbiotic diazotrophic rhizobia or bacteria in root organs known as nodules. Such nodule symbiosis occurs in 10 plant lineages in four taxonomic orders: Fabales, Fagales, Cucurbitales, and Rosales, which are collectively known as the nitrogen-fixing clade. Nodules are divided into two types based on differences in ontogeny and histology: legume-type and actinorhizal-type nodules.

The Non-Legume Mediates the Fitness of Nitrogen-Fixing Rhizobial Symbionts Under High Nitrogen Conditions.

Organisms rely on symbiotic associations for metabolism, protection, and energy. However, these intimate partnerships can be vulnerable to exploitation. What prevents microbial mutualists from parasitizing their hosts? In legumes, there is evidence that hosts have evolved sophisticated mechanisms to manage their symbiotic rhizobia, but the generality and evolutionary origins of these control mechanisms are under debate.

A Roadmap toward Engineered Nitrogen-Fixing Nodule Symbiosis.

In the late 19 century, it was discovered that legumes can establish a root nodule endosymbiosis with nitrogen-fixing rhizobia. Soon after, the question was raised whether it is possible to transfer this trait to non-leguminous crops. In the past century, an ever-increasing amount of knowledge provided unique insights into the cellular, molecular, and genetic processes controlling this endosymbiosis.

Mutant analysis in the nonlegume Parasponia andersonii identifies NIN and NF-YA1 transcription factors as a core genetic network in nitrogen-fixing nodule symbioses.

●Nitrogen-fixing nodulation occurs in 10 taxonomic lineages, with either rhizobia or Frankia bacteria. To establish such an endosymbiosis, two processes are essential: nodule organogenesis and intracellular bacterial infection. In the legume-rhizobium endosymbiosis, both processes are guarded by the transcription factor NODULE INCEPTION (NIN) and its downstream target genes of the NUCLEAR FACTOR Y (NF-Y) complex.

The Medicago truncatula nodule identity gene MtNOOT1 is required for coordinated apical-basal development of the root.

Background: Legumes can utilize atmospheric nitrogen by hosting nitrogen-fixing bacteria in special lateral root organs, called nodules. Legume nodules have a unique ontology, despite similarities in the gene networks controlling nodule and lateral root development. It has been shown that Medicago truncatula NODULE ROOT1 (MtNOOT1) is required for the maintenance of nodule identity, preventing the conversion to lateral root development.

Transforming, Genome Editing and Phenotyping the Nitrogen-fixing Tropical Cannabaceae Tree Parasponia andersonii.

Parasponia andersonii is a fast-growing tropical tree that belongs to the Cannabis family (Cannabaceae). Together with 4 additional species, it forms the only known non-legume lineage able to establish a nitrogen-fixing nodule symbiosis with rhizobium. Comparative studies between legumes and P.

GeneNoteBook, a collaborative notebook for comparative genomics.

Summary: Analysis and comparison of genomic and transcriptomic datasets have become standard procedures in biological research. However, for non-model organisms no efficient tools exist to visually work with multiple genomes and their metadata, and to annotate such data in a collaborative way. Here we present GeneNoteBook: a web based collaborative notebook for comparative genomics.

A Remote -Regulatory Region Is Required for Expression in the Pericycle to Initiate Nodule Primordium Formation in .

The legume-rhizobium symbiosis results in nitrogen-fixing root nodules, and their formation involves both intracellular infection initiated in the epidermis and nodule organogenesis initiated in inner root cell layers. () is a nodule-specific transcription factor essential for both processes. These NIN-regulated processes occur at different times and locations in the root, demonstrating a complex pattern of spatiotemporal regulation.

A Resurrected Scenario: Single Gain and Massive Loss of Nitrogen-Fixing Nodulation.

Root nodule endosymbiosis with nitrogen-fixing bacteria provides plants with unlimited access to fixed nitrogen, but at a significant energetic cost. Nodulation is generally considered to have originated in parallel in different lineages, but this hypothesis downplays the genetic complexity of nodulation and requires independent recruitment of many common features across lineages. Recent phylogenomic studies revealed that genes that function in establishing or maintaining nitrogen-fixing nodules are independently lost in non-nodulating relatives of nitrogen-fixing plants.

Comparative genomics of the nonlegume reveals insights into evolution of nitrogen-fixing rhizobium symbioses.

Nodules harboring nitrogen-fixing rhizobia are a well-known trait of legumes, but nodules also occur in other plant lineages, with rhizobia or the actinomycete as microsymbiont. It is generally assumed that nodulation evolved independently multiple times. However, molecular-genetic support for this hypothesis is lacking, as the genetic changes underlying nodule evolution remain elusive.

A genetically and functionally diverse group of non-diazotrophic Bradyrhizobium spp. colonizes the root endophytic compartment of Arabidopsis thaliana.

Background: Diazotrophic Bradyrhizobium spp. are well known for their ability to trigger nodule formation on a variety of legume species. In nodules, Bradyrhizobium utilizes plant-derived carbohydrates in exchange for fixed nitrogen.

CRISPR/Cas9-Mediated Mutagenesis of Four Putative Symbiosis Genes of the Tropical Tree Reveals Novel Phenotypes.

represents five fast-growing tropical tree species in the Cannabaceae and is the only plant lineage besides legumes that can establish nitrogen-fixing nodules with rhizobium. Comparative analyses between legumes and allows identification of conserved genetic networks controlling this symbiosis. However, such studies are hampered due to the absence of powerful reverse genetic tools for .