IN VITRO AND IN SILICO ANALYSIS OF TWO STREPTOMYCES SP. ISOLATED FROM SOYBEAN PLANTS WITH POTENTIAL AS PLANT GROWTH-PROMOTING BACTERIA.

VILLAFAÑES, D; GRAMAJO, H.; CHIESA; M.A.; RODRIGUEZ, E

Los Cocos, Cordoba

Congreso; XVII Congreso Argentino de Microbiología General; 2022

Sociedad Argentina de Microbiología General, SAMIGE

Nowadays, there is a need to develop sustainable and eco-friendly strategies for cropproduction, with the aim of minimizing the use of agrochemicals. The utilization of soilbeneficial microbes as plant growth-promoters has been proved to be one of the mainalternatives. Bacteria belonging to the genus Streptomyces have been considered apromising group to improve plant growth and protect them from severalphytopathogens. However, their role as plant-growth promoter bacteria (PGPB) is notdeeply understood. The main objective of this work was to characterize strains ofStreptomyces sp. isolated from soybean [Glycine max (L.) Merr] plants and itsrizosphere for their potential application as plant growth promoters and biocontrolagents. Thus, 78 actinobacteria, mainly belonging to the genus Streptomyces, wereisolated from soybean plants cultivated in the core productive area of Argentina. First,their antagonistic effect against some of the principal phytopathogenic fungi thatthreaten this crop was tested. Only 12 (15%) showed good in vitro antifungal activities.Then, in order to select the strains with the best PGPB properties, they were furtheranalyzed through different in vitro assays. The ability to produce chitinases,siderophores, indole-3 acetic acid (IAA) and to solubilize inorganic phosphate, allowedthe selection of the two most promising strains as PGPB. In order to deeply understandthe mechanisms involved, their genomes were sequenced and the sets of genescontributing to these plant-beneficial functions were analyzed. Bioinformatic analysisrevealed the presence of genes encoding putative alkaline and acid phosphatasespossibly implicated in the solubilization of inorganic phosphate. Alsoexopolyphosphatases and polyphosphate kinases were detected, two key enzymesinvolved in the accumulation of polyphosphates in microbes. Six chitinase-encodinggenes were found, one of them belonging to the GH-19 family, a group of enzymesimplicated in the plant defense response against fungal pathogens invasions. Despitethe in vitro production of IAA, none of the conventional biosynthetic pathways could becompletely reconstructed in silico. A group of genes related to the iron acquisition andmetabolism and the biosynthesis of different polyamines were identified. Moreover, inplanta experiments under greenhouse conditions have shown a significant promotion ofgermination and emergence process as well as high protection indexes againstDiaporthe aspalathi, causal agent of Stem Canker in soybean. Finally, mutagenesis ofdifferent identified genes will be performed in order to validate the role of each one inthe PGPB properties of these Streptomyces sp