Chemical signaling during Delftia-Sinorhizobium-alfalfa interaction

MOREL, M., CASTRO-SOWINSKI, S., DARDANELLI, M.S.

Geneva, Switzerland.

Congreso; 4th Congress of European Microbiologists; 2011

European Microbiologists Association

Delftia sp. JD2 is a plant-growth-promoting bacterium (PGPB) that produces 3-indol-acetic acid (IAA) and promotes the growth of Medicago sativa (alfalfa), among other PGPB capabilities. In addition, JD2 increases plant yield and nodulation rate when is co-inoculated with rizobial strains, in gnotobiotic experiments. With the aim to identify the chemical signals involved during the plant-bacteria communication, we analyzed flavonoids, carbohydrates, lipids and IAA composition of roots exudates of alfalfa. Plants were inoculated and co-inoculated with Sinorhizobium meliloti U143 and Defltia sp. JD2 in hydroponic experiments. Changes in the profile of flavonoids were analyzed at 4, 7 and 15 days after inoculation by LC/MS/MS and, carbohydrates and lipids were detected by GC. We are currently interested in understanding how JD2 interact with alfalfa and persuade it of their good intentions as a PGPB. Y eL IAA? We detected an increased secretion of luteolin (flavone) and isoflavones, as well as some sugars and lipids, during co-inoculation compared to single inoculation. Luteolin is the main flavonoid produced by alfalfa and is recognized as an inducer of the rizobial nodulation genes. This increased secretion of flavonoids, carbohydrates and lipids was detected during the first days of the bacteria-plant interaction. The data presented indicate that, during co-inoculation, JD2 could induce the secretion of flavonoids involved in an efficient rizobial infective process. The possible changes in flavonoid, carbohydrates and lipids profiles detected will be discussed in the presentation of this work.