Aeromonas punctata PNS-1: a promising candidate to change the root morphogenesis of Arabidopsis thaliana in MS and sand system

A model system of sand, comprising Arabidopsis plants inoculated with Aeromonas punctata PNS-1 strain, was used to evaluate the bacterial effect in modulation of plant root structure at second-order lateral root level. In MS media, the root morphogenesis was changed only at first-order lateral root level when inoculated with PNS-1 strain. Inoculation with PNS-1 strain was subjected to significant (P < 0.01) increase in primary root length and lateral root density in both MS and sand system. However, this strain modulated the root structure in the sand environment in a complex manner that may be helpful for incitation of the plant–microbe interaction close to natural environment. In order to determine whether this change in root morphology was due to bacterial auxin, Arabidopsis transgenic line (DR5:GUS) was used to reveal the change in homeostasis of endogenous auxin. In PNS-1 inoculated transgenic seedlings of Arabidopsis plant (DR5:GUS), endogenous auxin in primary root apices and lateral roots was enhanced. For confirmation, PNS-1 was evaluated for auxin production in vitro, showed an increase in auxin production after supplementation of l-tryptophan. The presence of ACC deaminase activity in PNS-1 showed its possible involvement in primary root elongation. In the present study Aeromonas punctata PNS-1 is the potential candidate for triggering the change in root morphogenesis of Arabidopsis thaliana with the involvement of auxin and ACC deaminase production.