The modification of the flavonoid naringenin by Bradyrhizobium sp. strain ORS285 change the nod genes inducer function to a growth stimulator

• Published in: Molecular plant-microbe interactions
• Main Authors: Nouwen, Nico, Gargani, Daniel, Giraud, Eric
• Format: Journal Article
• Language: English
• Published: United States 02-07-2019
• ISSN: 0894-0282

As inducers of nodulation (
) genes, flavonoids play an important role in the symbiotic interaction between rhizobia and legumes. However, besides the control of expression of
genes many other effects of flavonoids on rhizobial cells have been described. Here, we showed that the flavonoid naringenin stimulates the growth of the photosynthetic
sp. strain ORS285. This growth stimulating effect was still observed with ORS285 strains deleted for
,
or naringenin degrading
operon. Phenotypic microarray analysis indicated that in the cells grown in presence of naringenin, the glycerol and fatty acid metabolism is activated. Moreover, electron microscopic and enzymatic analysis showed that polyhydroxy alkanoate metabolism is altered in naringenin grown cells. Whereas strain ORS285 is able to degrade naringenin, a fraction is converted into an intense yellow coloured molecule with a
(+) of 363.0716. Further analysis, indicated that this molecule is a hydroxylated and O-methylated form of naringenin. In contrast to naringenin, this derivative does not induce
gene expression but it does stimulate the growth of strain ORS285. We hypothesize that the growth stimulation and metabolic changes induced by naringenin are part of a mechanism to facilitate the colonization and infection of naringenin exuding host plants.