Figure 1: Rhizophagus irregularis colonizing a tomato root and stained with WGA-Alexa Fluor 488. Intraradical hyphae grow inside the root eventually forming arbuscules (highly branched hyphal structures) inside inner cortex root cells where the nutrient exchange between the two symbionts takes place.
Figure 2: UMAP displaying different cell clusters of tomato roots colonized by Rhizophagus irregularis. The cluster corresponding to cells housing fungal arbuscules can be seen arising from the cortical cell cluster.

Arbuscular mycorrhizal fungi (AMF) form mutualistic associations with more than 80% of all land plants. AMF provide their host plants with essential nutrients such as phosphate, in return for plant derived carbohydrates. Hence, AMF could be used in agriculture to lower the use of chemical fertilizers. However, much is still not known about this complex plant-fungal interaction. Our research focusses on the molecular mechanisms of both symbiotic partners to establish and maintain the mutualistic relationship.

AMF effector proteins:

From the plant pathology field, we know that the secretion of small effector proteins is used to repress immune signaling and to create a suitable niche for the pathogen. Interestingly, AM fungi are also predicted to secrete effectors but little is known about their role inside the plant as well as their interacting plant proteins during AM symbiosis. In this research, we focus on the model species Rhizophagus irregularis with its host tomato. We aim to learn how these AM effectors function inside the host plant, by identifying their plant protein partners and elucidating how this interaction alters plant growth during mycorrhization under control and diverse stress conditions such as drought and nutrient limitations. Via high-throughput analyses of direct interactions by means of Y2H-Seq as well as complex purification methods such as GFP trapping and proximity labeling, we want to identify the protein-protein interplay during the development of AMF-tomato symbiosis.

Plant defense and nutrient exchange:

Our focus lies in deciphering the genetic mechanisms of the symbiosis between Rhizophagus irregularis and tomato, particularly sugar metabolism, signaling, and plant defense responses. By employing single nuclei RNA sequencing, we dissect the gene expression profiles at the single cell level, providing insights into the complex regulation of this symbiosis with an unprecedented depth. We aim to identify and functionally characterize key molecular players in the regulation of plant defense and nutrient exchange throughout the symbiosis.