Research focus

Marcelle Holsters left VIB on 1 Jan 2012. This page will no longer be updated

​Our research aims to understand the molecular mechanisms that govern the co-habitation between host plants and endophytic bacteria. The questions we address refer to plant growth and development, cell death, division and differentiation in the specific biological context of adaptation and cross-talk between two organisms that influence each other’s behavior.

Which signals do the partners emit? How do they affect each other’s gene expression to redirect growth and development? How do endophytic bacteria enter the tissues of their hosts? How do they manage to survive, and which factors mediate the establishment of co-habitation equilibrium?

The group has a long-standing interest in the nitrogen-fixing Rhizobium-legume symbiosis, with a focus on formation of a new organ primordium, the nodule primordium, the mechanism of bacterial entry and the plant control of the nitrogen-fixation phase. We study the interaction between the tropical, semi-aquatic legume Sesbania rostrata and its microsymbiont Azorhizobium caulinodans, comparing two different invasion pathways that occur on this host as an adaptation to water-tolerant growth and nodulation.

We recently introduced the model legume Medicago truncatula in our laboratory and studied the role of transcription factors in early nodulation events. In particular, we want to make a molecular comparison between nodule primordium initiation and lateral root formation. In parallel, a project on nodule senescence was initiated. This new direction creates links with other divisions in the department and with the European M. truncatula research community, and prepares us for a future systems biology approach to legume symbiosis.  
   
The second line of research is the analysis of the co-habitation between the biotrophic, endophytic Gram-positive bacterium Rhodococcus fascians and its host plants. The focus is on bacterial signaling to redirect plant growth and on the analysis of the transcriptional responses of the host. For most of our microscopic and physiological studies, Nicotiana tabacum has been the host of choice, but to address the molecular reaction of the plant to the presence of R. fascians we study Arabidopsis thaliana, making use of the functional genomics tools and facilities available in the department.