– Part of the CDA Fall Lecture Series.

Speaker: Paul Schulze-Lefert

Department of Plant-Microbe Interactions

Max Planck Institute for Plant Breeding Research

Theme

Symbiosis – hosted by Prof. Brande Wulff

Abstract

Healthy plants in nature are colonized by multi-kingdom microbial communities including bacteria and fungi, termed the plant microbiota, which promote plant growth and health. Our work focuses on the root microbiota and aims at a deeper understanding of the mechanisms underlying the establishment of root-associated microbial communities and their beneficial functions for the host.  We have established systematic culture collections of the root microbiota of the crucifer Arabidopsis thaliana and the legume Lotus japonicus, allowing us to purify the majority of bacterial and fungal taxa associated with healthy roots. We then compose defined consortia, so-called synthetic communities (SynComs), from the isolated root commensals and reconstitute the root microbiota in co-cultivation experiments with germ-free plants to study physiological community functions in laboratory environments. Using taxonomically paired synthetic communities from L. japonicus and A. thaliana in a multi-species gnotobiotic system, we detect clear signatures of host preference among commensal bacteria in a community context, but not in mono-associations. Sequential inoculation of either host reveals strong priority effects during the assembly of the root microbiota, where established communities are resilient to invasion by late-comers. However, we found that host preference by commensal bacteria confers a competitive advantage in their native host. We reveal that host preference is prevalent in commensal bacteria from diverse taxonomic groups and that this trait is directly linked to their invasiveness into standing root-associated communities. In another line of research, we have shown that under iron deprivation, the secretion of coumarins from A. thaliana roots into the rhizosphere is essential for a beneficial interaction with the bacterial root microbiota. In particular, the microbiota improves iron-limiting plant performance via a mechanism dependent on plant iron import and secretion of the coumarin fraxetin. This beneficial trait is strain specific yet functionally redundant across phylogenetic lineages of the microbiota. We propose that the bacterial root microbiota, stimulated by secreted coumarins, is an integral mediator of plant adaptation to iron-limiting soils. 

About the Speaker

Paul Schulze-Lefert trained in biochemistry and genetics at the Universities of Marburg, Freiburg, and Cologne, in Germany. After his Ph.D. thesis on light regulation in plants, he became interested in the molecular processes underlying plant-microbe interactions. In 1991 he started his own research group at the RWTH Aachen, Germany, with a focus on plant disease resistance mechanisms to fungal pathogens. From 1995 to 2000 he was based at the Sainsbury Laboratory at the John Innes Centre, in England. Since 2000 he has been the Director and a Scientific Member at the Max Planck Institute for Plant Breeding Research, in Cologne, and since 2003 an Honorary Professor at Cologne University. Paul is an elected member of EMBO, the National Academy of Sciences, USA, the German National Academy of Sciences, Leopoldina, and of the American Academy of Microbiology, USA. He is a science advisory board member of the Two Blades Foundation and a co-founder and advisor of AgBiome, a for-profit company that explores the crop microbiome to develop biologicals that improve plant health and productivity.