Identification and Characterization of Common Bean () Non-Nodulating Mutants Altered in Rhizobial Infection.

The symbiotic N-fixation process in the legume-rhizobia interaction is relevant for sustainable agriculture. The characterization of symbiotic mutants, mainly in model legumes, has been instrumental for the discovery of symbiotic genes, but similar studies in crop legumes are scant. To isolate and characterize common bean () symbiotic mutants, an ethyl methanesulphonate-induced mutant population from the BAT 93 genotype was analyzed.

Impact of c-di-GMP on the Extracellular Proteome of .

Extracellular matrix components of bacterial biofilms include biopolymers such as polysaccharides, nucleic acids and proteins. Similar to polysaccharides, the secretion of adhesins and other matrix proteins can be regulated by the second messenger cyclic diguanylate (cdG). We have performed quantitative proteomics to determine the extracellular protein contents of a strain expressing high cdG intracellular levels.

A Tar aspartate receptor and Rubisco-like protein substitute biotin in the growth of rhizobial strains.

Biotin is a key cofactor of metabolic carboxylases, although many rhizobial strains are biotin auxotrophs. When some of these strains were serially subcultured in minimal medium, they showed diminished growth and increased excretion of metabolites. The addition of biotin, or genetic complementation with biotin synthesis genes resulted in full growth of CFN42 and CIAT652 strains.

Control of the Rhizobia Nitrogen-Fixing Symbiosis by Common Bean MADS-Domain/AGL Transcription Factors.

Plants MADS-domain/AGL proteins constitute a large transcription factor (TF) family that controls the development of almost every plant organ. We performed a phylogeny of (. 500) MADS-domain proteins from Arabidopsis and four legume species.

A Novel OmpR-Type Response Regulator Controls Multiple Stages of the N-Fixing Symbiosis.

OmpR, is one of the best characterized response regulators families, which includes transcriptional regulators with a variety of physiological roles including the control of symbiotic nitrogen fixation (SNF). The CE3 genome encodes 18 OmpR-type regulators; the function of the majority of these regulators during the SNF in common bean, remains elusive. In this work, we demonstrated that a mutant strain lacking the OmpR-type regulator RetPC57 (ΔRetPC57), formed less nodules when used as inoculum for common bean.

Genetic regulation, biochemical properties and physiological importance of arginase from .

In bacteria, l-arginine is a precursor of various metabolites and can serve as a source of carbon and/or nitrogen. Arginine catabolism by arginase, which hydrolyzes arginine to l-ornithine and urea, is common in nature but has not been studied in symbiotic nitrogen-fixing rhizobia. The genome of the alfalfa microsymbiont 1021 has two genes annotated as arginases, () and ().

Produces Nitrous Oxide by Coupling the Assimilatory and Denitrification Pathways.

More than two-thirds of the powerful greenhouse gas nitrous oxide (NO) emissions from soils can be attributed to microbial denitrification and nitrification processes. Bacterial denitrification reactions are catalyzed by the periplasmic (Nap) or membrane-bound (Nar) nitrate reductases, nitrite reductases (NirK/ Nir), nitric oxide reductases (cNor, qNor/ CuNor), and nitrous oxide reductase (Nos) encoded by /, , and genes, respectively. CFN42, the microsymbiont of common bean, is unable to respire nitrate under anoxic conditions and to perform a complete denitrification pathway.

Conjugative transfer between Rhizobium etli endosymbionts inside the root nodule.

Since the discovery that biological nitrogen fixation ensues in nodules resulting from the interaction of rhizobia with legumes, nodules were thought to be exclusive for hosting nitrogen-fixing and plant growth promoting bacteria. In this work, we uncover a novel function of nodules, as a niche permissive to acquisition of plasmids via conjugative transfer. We used Rhizobium etli CFN42, which nodulates Phaseolus vulgaris.

Phosphate Deficiency Negatively Affects Early Steps of the Symbiosis between Common Bean and Rhizobia.

Phosphate (Pi) deficiency reduces nodule formation and development in different legume species including common bean. Despite significant progress in the understanding of the genetic responses underlying the adaptation of nodules to Pi deficiency, it is still unclear whether this nutritional deficiency interferes with the molecular dialogue between legumes and rhizobia. If so, what part of the molecular dialogue is impaired? In this study, we provide evidence demonstrating that Pi deficiency negatively affects critical early molecular and physiological responses that are required for a successful symbiosis between common bean and rhizobia.

Analysis of genome sequence and symbiotic ability of rhizobial strains isolated from seeds of common bean (Phaseolus vulgaris).

Background: Rhizobia are alpha-proteobacteria commonly found in soil and root nodules of legumes. It was recently reported that nitrogen-fixing rhizobia also inhabit legume seeds. In this study, we examined whole-genome sequences of seven strains of rhizobia isolated from seeds of common bean (Phaseolus vulgaris).

Characterization of the Symbiotic Nitrogen-Fixing Common Bean Low Phytic Acid (lpa1) Mutant Response to Water Stress.

The common bean ( L.) () biofortified genotype produces seeds with improved nutritional characteristics and does not display negative pleiotropic effects. Here we demonstrated that plants establish an efficient nitrogen-fixing symbiosis with CE3.

Overproduction of Sinorhizobium meliloti ArgC (N-acetyl-gamma-glutamyl phosphate reductase) promotes growth delay and inefficient nodules.

argC encodes N-acetyl-gamma-glutamyl phosphate reductase, the enzyme that catalyzes the high-energy-consuming third step in the arginine synthesis pathway. A comparative analysis revealed two translation start sites in argC from Sinorhizobium meliloti. To determine whether both protein versions are synthesized in the organism and their functional role, we obtained genetic constructs with one (1S) or two (2S) start sites, with promoters of low (pspeB) or high (plac) transcriptional rate.

Genomic studies of nitrogen-fixing rhizobial strains from Phaseolus vulgaris seeds and nodules.

Background: Rhizobia are soil bacteria that establish symbiotic relationships with legumes and fix nitrogen in root nodules. We recently reported that several nitrogen-fixing rhizobial strains, belonging to Rhizobium phaseoli, R. trifolii, R.

Expanding the regulatory network that controls nitrogen fixation in Sinorhizobium meliloti: elucidating the role of the two-component system hFixL-FxkR.

In Sinorhizobium meliloti, nitrogen fixation is regulated in response to oxygen concentration through the FixL-FixJ two-component system (TCS). Besides this conserved TCS, the field isolate SM11 also encodes the hFixL-FxkR TCS, which is responsible for the microoxic response in Rhizobium etli. Through genetic and physiological assays, we evaluated the role of the hFixL-FxkR TCS in S.

Genetic and biochemical characterization of arginine biosynthesis in Sinorhizobium meliloti 1021.

L-Ornithine production in the alfalfa microsymbiont Sinorhizobium meliloti occurs as an intermediate step in arginine biosynthesis. Ornithine is required for effective symbiosis but its synthesis in S. meliloti has been little studied.

The micro-RNA72c-APETALA2-1 node as a key regulator of the common bean-Rhizobium etli nitrogen fixation symbiosis.

Micro-RNAs are recognized as important posttranscriptional regulators in plants. The relevance of micro-RNAs as regulators of the legume-rhizobia nitrogen-fixing symbiosis is emerging. The objective of this work was to functionally characterize the role of micro-RNA172 (miR172) and its conserved target APETALA2 (AP2) transcription factor in the common bean (Phaseolus vulgaris)-Rhizobium etli symbiosis.

Nitrogen-fixing rhizobial strains isolated from common bean seeds: phylogeny, physiology, and genome analysis.

Rhizobial bacteria are commonly found in soil but also establish symbiotic relationships with legumes, inhabiting the root nodules, where they fix nitrogen. Endophytic rhizobia have also been reported in the roots and stems of legumes and other plants. We isolated several rhizobial strains from the nodules of noninoculated bean plants and looked for their provenance in the interiors of the seeds.

Zn-bis-glutathionate is the best co-substrate of the monomeric phytochelatin synthase from the photosynthetic heavy metal-hyperaccumulator Euglena gracilis.

The phytochelatin synthase from photosynthetic Euglena gracilis (EgPCS) was analyzed at the transcriptional, kinetic, functional, and phylogenetic levels. Recombinant EgPCS was a monomeric enzyme able to synthesize, in the presence of Zn(2+) or Cd(2+), phytochelatin2-phytochelatin4 (PC2-PC4) using GSH or S-methyl-GS (S-methyl-glutathione), but not γ-glutamylcysteine or PC2 as a substrate. Kinetic analysis of EgPCS firmly established a two-substrate reaction mechanism for PC2 synthesis with Km values of 14-22 mM for GSH and 1.

Two common bean genotypes with contrasting response to phosphorus deficiency show variations in the microRNA 399-mediated PvPHO2 regulation within the PvPHR1 signaling pathway.

Crop production of the important legume, the common bean (Phaseolus vulgaris), is often limited by low phosphorus (P) in the soil. The genotypes, BAT477 and DOR364, of the common bean have contrasting responses to P starvation. Plants from the BAT477 P deficiency tolerant genotype showed higher phosphate content and root biomass as compared to the DOR364 plants under P starvation.

Transcript profiling of common bean nodules subjected to oxidative stress.

Several environmental stresses generate high amounts of reactive oxygen species (ROS) in plant cells, resulting in oxidative stress. Symbiotic nitrogen fixation (SNF) in the legume-rhizobia symbiosis is sensitive to damage from oxidative stress. Active nodules of the common bean (Phaseolus vulgaris) exposed to the herbicide paraquat (1,1'-dimethyl-4,4'-bipyridinium dichloride hydrate), which stimulates ROS accumulation, exhibited reduced nitrogenase activity and ureide content.

Common bean (Phaseolus vulgaris L.) PvTIFY orchestrates global changes in transcript profile response to jasmonate and phosphorus deficiency.

Background: TIFY is a large plant-specific transcription factor gene family. A subgroup of TIFY genes named JAZ (Jasmonate-ZIM domain) has been identified as repressors of jasmonate (JA)-regulated transcription in Arabidopsis and other plants. JA signaling is involved in many aspects of plant growth/development and in defense responses to biotic and abiotic stresses.