Postdoc Department of Biology and Howard Hughes Medical Institute, Duke University
Microbes are associated with every plant tissue. Plants continuously monitor the presence of microorganisms to establish an adapted response. Plants use pattern recognition receptors to perceive microbe associated molecular patterns (MAMPs), which are microorganism specific molecules. MAMP detection leads to an immune response called MAMP-triggered immunity (MTI). The plant immune system not only recognizes pathogenic bacteria but also beneficial bacteria. However, unlike immune recognition of pathogenic bacteria, which has been extensively studied, the interaction of beneficial bacteria with the plant immune system is less well explored. To address this knowledge gap, I studied the colonization of Arabidopsis thaliana by Bacillus valezensis, an auxin producing beneficial bacterium. Auxin is a central plant hormone, playing many roles during plant development. Bacteria-produced auxin has been shown to influence root development. However, the role played by auxin for the bacteria is less clear. I found that the plant immune system and bacteria-produced auxin stimulate each other. Bacteria trigger an immune reaction in the root, which, in turn, triggers auxin production by bacteria. Auxin promotes expansion of bacterial colonies over the root triggering further immune reaction. Thus, bacteria and the plant are engaged in a positive feedback loop promoting efficient root colonization by the bacteria and root developmental response.
Coauthors: Philip Benfey – Department of Biology and Howard Hughes Medical Institute, Duke University.