Role of Type V Protein Secretion System in endophytic rice root colonization by Azoarcus sp. BH72
M. MARSZALKOWSKA (1), A. Sarkar (1), M. Schäfer (2), B. Reinhold-Hurek (1) (1) Department of Microbe - Plant Interactions, University of Bremen, Germany; (2) John Innes Centre, United Kingdom

Endophytic interactions between beneficial bacteria and plants possess a great potential for application in agriculture, as they offer opportunities to modulate plant growth and nutrition. Recent studies revealed high relative abundance of type V protein secretion system (T5SS) genes in a rice endophyte metagenome, which indicate its important role in symbiotic plant-microbe interaction. However, little is known about the function of these proteins in endophytes. The genome of the diazotrophic rice-endophyte Azoarcus sp. BH72 harbors a single gene encoding a T5SS: azo1653. Microarray data and analysis of ß-glucuronidase transcriptional reporter gene fusions, have shown a significant up-regulation of expression azo1653 under microaerobic conditions. This up-regulation indicates a potential relevance of azo1653 in establishing the Azoarcus-rice cooperation, as endorhizosphere of flooded rice roots is characterized by low oxygen tensions. However, competition assays on rice roots revealed, that at the early stages of interaction, a BH1653 mutant strain attaches and colonizes roots more successfully than wild-type Azoarcus sp. BH72. This effect was reduced 14-days post-inoculation, as both strains exhibited similar colonization capacity. Surprisingly, a reverse trend was observed in single-strain inoculation experiments. This complex phenotype may suggest a novel role of T5SS proteins in endophyte-microbe interaction, with differential involvement in early and late responses.

Abstract Number: P2-13
Session Type: Poster