Dissecting the Cellular Control of Septin Organization in a Global Cereal Killer

Abstract

Rice blast disease, caused by the fungus Magnaporthe oryzae, destroys enough rice each year to feed 60 million people, and is a major threat to global food security. To establish disease, M. oryzae forms a specialized infection structure called an appressorium, which it uses to physically break into rice leaves. Essential for this process is the timely assembly of a septin ring structure at the base of the appressorium. Septins are a conserved family of GTP‐binding proteins, forming hetero‐oligomeric rods and filaments that are organized into higher‐order structures at the cell cortex. The M. oryzae septin ring scaffolds the formation of a donut‐shaped filamentous actin network, needed for the emergence of a polarized penetration structure from the base of the appressorium. Importantly, relatively little is understood about how higher‐order septin structures form in the right place and at the right time in appressoria to drive infection. We are using a proximity‐dependent proteomics to identify novel proteins involved in septin organization, and are functionally characterizing these using reverse genetics, and cell biological approach. We genetically tagged the septin protein Cdc11/Sep5 with TurboID, and identified a host of putatively proximal and interacting proteins. Here, we validate a number of these, and investigate their broader role in fungal biology. The outcomes of this research will provide fundamental new insight into the cellular control of septin organization in a global cereal killer.