Arbuscular mycorrhiza (AM) are mutualistic interactions formed between soil fungi and plant roots. AM symbiosis is a fundamental and widespread trait in plants with the potential to sustainably enhance future crop yields. However, improving AM fungal association in crop species requires a fundamental understanding of host colonization dynamics across varying agronomic and ecological contexts. To this end, Timoneda, Yunusov et al. demonstrate the use of betalain pigments as in vivo visual markers for the occurrence and distribution of AM fungal colonization by the mycorrhizal fungus Rhizophagus irregularis in roots of the plants Medicago truncatula and Nicotiana benthamiana. Using established and novel AM-responsive promoters, the authors assembled multigene reporter constructs that enable the AM-controlled expression of the core betalain synthesis genes. Ultimately, they present MycoRed, a useful innovative method that they hope will expand and complement currently used fungal visualization techniques to advance knowledge in the field of AM symbiosis. The image shows a plant root producing red betalains in cells colonized by symbiotic arbuscular mycorrhiza fungi.

Image Credit: Temur Yunusov and Alfonso Timoneda