Does the root extracellular trap affect the accessibility of microorganisms to the root tip?

Fabaceae are important crops for their protein-rich seeds, which are essential for human and animal nutrition. They also play a significant role in agriculture as green manures or in crop rotations by fixing atmospheric nitrogen through root symbiosis with rhizobacteria, thus reducing the need for nitrogen fertilizers. This is exemplified by soybean (Glycine max) and pea (Pisum sativum). Plant development and health largely depend on root-microorganism interactions. The root tip and root-Associated Cap-Derived Cells (AC-DCs) release various organic compounds into the rhizosphere, forming the Root Extracellular Trap (RET), a network involved in root-soil microorganism interactions and protection. This study investigates the role of soybean and pea RETs in interactions with soil microorganisms (Bacillus subtilis, Pseudomonas fluorescens and Phytophthora parasitica zoospores) by examining their impact on microbial behavior. Results show that the RET alters microbial access to the root tip and significantly modifies speeds and trajectories. Inside the RET, the speeds of B. subtilis and P. parasitica zoospores decreased three and nine times, respectively. Outside the RET, the speed of the bacterium remains unchanged, while that of the zoospores decreases twice. These findings highlight the influence of the RET on microbial movement and its importance in plant-microorganism interactions in the rhizosphere.