Project description:Herbaspirillum seropedicae is an endophytic bacterium that can fix nitrogen and promote a hormonal imbalance that leads to a plant growth-promoting effect when used as a microbial inoculant. Studies focused on mechanisms of action are crucial for a better understanding of the bacteria-plant interaction and optimization of plant growth-promoting response. The work aims to understand the underlined mechanisms responsible for the early stimulatory growth effects of the H. seropedicae inoculation in maize. To perform it, we combined transcriptomic and proteomic approaches with physiological analysis. The results obtained with the inoculation showed increased root biomass (233 and 253%) and shoot biomass (249 and 264%), respectively, for the fresh and dry mass of maize seedlings and increased green content and development. Omics data analysis for the positive biostimulation phenotype revealed that inoculation increases N-uptake and N-assimilation machinery through differential expressed nitrate transporters and amino acids pathway, as well carbon/nitrogen metabolism integration by the tricarboxylic acid cycle and the polyamines pathway. Additionally, phytohormone levels of root and shoot tissues increased in bacterium-inoculated-maize plants leading to feedback regulation by the ubiquitin-proteasome system. The early biostimulatory effect of H. seropedicae partially results from hormonal imbalance coupled with efficient nutrient uptake-assimilation and a boost in primary anabolic metabolism of carbon-nitrogen integrative pathways.
Project description:H. seropedicae is a diazotrophic and endophytic bacterium that associates with economically important grasses promoting plant growth and increasing productivity. To identify genes related to bacterial ability to colonize and promote plant growth wheat seedlings growing hydroponically in Hoaglandâs medium were inoculated with H. seropedicae the bacteria and incubated for 3 days. mRNA from the bacteria present in the root surface and in the plant medium were purified, depleted from rRNA and used for RNA-seq profiling. RT-qPCR analyses were conducted to confirm regulation of selected genes. Comparison of RNA profile of bacteria attached to the root and planktonic revealed an extensive metabolic adaptation to the epiphytic life style.
Project description:Most Herbaspirillum seropedicae strains are beneficial endophytes to plants. In contrast, H. seropedicae strain Os34, isolated from rice roots, is pathogenic. The draft genome sequence of strain Os34 presented here allows in-depth comparative genome analyses to understand the specific mechanisms of beneficial and pathogenic Herbaspirillum-plant interactions.
Project description:The molecular mechanisms of plant recognition, colonization, and nutrient exchange between diazotrophic endophytes and plants are scarcely known. Herbaspirillum seropedicae is an endophytic bacterium capable of colonizing intercellular spaces of grasses such as rice and sugar cane. The genome of H. seropedicae strain SmR1 was sequenced and annotated by The Paraná State Genome Programme--GENOPAR. The genome is composed of a circular chromosome of 5,513,887 bp and contains a total of 4,804 genes. The genome sequence revealed that H. seropedicae is a highly versatile microorganism with capacity to metabolize a wide range of carbon and nitrogen sources and with possession of four distinct terminal oxidases. The genome contains a multitude of protein secretion systems, including type I, type II, type III, type V, and type VI secretion systems, and type IV pili, suggesting a high potential to interact with host plants. H. seropedicae is able to synthesize indole acetic acid as reflected by the four IAA biosynthetic pathways present. A gene coding for ACC deaminase, which may be involved in modulating the associated plant ethylene-signaling pathway, is also present. Genes for hemagglutinins/hemolysins/adhesins were found and may play a role in plant cell surface adhesion. These features may endow H. seropedicae with the ability to establish an endophytic life-style in a large number of plant species.
Project description:BackgroundThe PII protein family comprises homotrimeric proteins which act as transducers of the cellular nitrogen and carbon status in prokaryotes and plants. In Herbaspirillum seropedicae, two PII-like proteins (GlnB and GlnK), encoded by the genes glnB and glnK, were identified. The glnB gene is monocistronic and its expression is constitutive, while glnK is located in the nlmAglnKamtB operon and is expressed under nitrogen-limiting conditions.ResultsIn order to determine the involvement of the H. seropedicae glnB and glnK gene products in nitrogen fixation, a series of mutant strains were constructed and characterized. The glnK- mutants were deficient in nitrogen fixation and they were complemented by plasmids expressing the GlnK protein or an N-truncated form of NifA. The nitrogenase post-translational control by ammonium was studied and the results showed that the glnK mutant is partially defective in nitrogenase inactivation upon addition of ammonium while the glnB mutant has a wild-type phenotype.ConclusionsOur results indicate that GlnK is mainly responsible for NifA activity regulation and ammonium-dependent post-translational regulation of nitrogenase in H. seropedicae.
Project description:Most Herbaspirillum seropedicae strains are beneficial to plants. In contrast, H. seropedicae strain Os45, isolated from rice roots, is pathogenic. The draft genome sequence of strain Os45 presented here allows an in-depth comparative genome analysis to understand the subtle mechanisms of beneficial and pathogenic Herbaspirillum-plant interactions.
Project description:This project defines the exoproteome dynamics of Frankia coriariae, a nitrogen-fixing bacterium, in presence of three host plants. Frankia coriariae was treated with root exudates from compatible (Coriaria myrtifolia), incompatible (Alnus glutinosa) and non-actinorhizal (Cucumis melo) host plants.
Project description:This project contributes to define the proteome dynamics of Frankia coriariae, a nitrogen-fixing bacterium, in presence of three host plants. Frankia coriariae was treated with root exudates from compatible (Coriaria myrtifolia), incompatible (Alnus glutinosa) and non-actinorhizal (Cucumis melo) host plants.