New insights into auxin metabolism in Bradyrhizobium japonicum

Publication date: Available online 8 May 2018Source: Research in MicrobiologyAuthor(s): Daniela Torres, Iliana Benavidez, Florencia Donadio, Elias Mongiardini, Susana Rosas, Stijn Spaepen, Jozef Vanderleyden, Aleš Pěnčík, Ondřej Novák, Miroslav Strnad, Jitka Frébortová, Fabricio CassánAbstractBacterial metabolism of phytohormones includes several processes such as biosynthesis, catabolism, conjugation, hydrolysis and homeostatic regulation. However, only biosynthesis and occasionally catabolism are studied in depth in microorganisms. In this work, we evaluated and reconsidered IAA metabolism in Bradyrhizobiumjaponicum E109, one of the most widely used strains for soybean inoculation around the world. The genomic analysis of the strain showed the presence of several genes responsible for IAA biosynthesis, mainly via indole-3-acetonitrile (IAN), indole-3-acetamide (IAM) and tryptamine (TAM) pathways. However; in vitro experiments showed that IAA is not accumulated in the culture medium in significant amounts. On the contrary, a strong degradation activity was observed after exogenous addition of 0.1 mM of IAA, IBA or NAA to the medium. B. japonicum E109 was not able to grow in culture medium containing IAA as a sole carbon source. In YEM medium, the bacteria degraded IAA and hydrolyzed amino acid auxin conjugates with alanine (IAAla), phenylalanine (IAPhe), and leucine (IAPhe), releasing IAA which was quickly degraded. Finally, the presence of exogenous IAA induced ...

Source: Research in Microbiology - July 10, 2018 Category: Microbiology Source Type: research