Methods and Advances in Legume Mutualistic Symbioses

TOPICAL COLLECTIONS

Guest Editors

Chandan Kumar Gautam

North Dakota State University

Dr. Chandan Gautam is a principal research associate in the Department of Microbiological Sciences at North Dakota State University. His research integrates molecular biology, physiology, and synthetic biology to develop microbial and plant-based sustainable solutions for improved nutrient acquisition. He earned his PhD through the Taiwan International Graduate Program fellowship at Academia Sinica and National Chung Hsing University in Taiwan, where he investigated how Arabidopsis coordinates iron-deficiency responses under varying pH conditions. He completed postdoctoral training with Dr. Lena Müller at the University of Miami, where he studied arbuscular mycorrhizal (AM) symbiosis and nutrient signaling networks in plants, and with Dr. Barney Geddes at North Dakota State University, where he worked on engineering root nodule symbiosis in cereal crops. He has also served on the Program Committee of the American Society of Plant Biologists (ASPB).

Chinh X. Luu

North Dakota State University

Dr. Chinh Luu is a postdoctoral research fellow in the Department of Microbiological Sciences at North Dakota State University. His research focuses on designing and incorporating nitrogen fixation biosensors into high-throughput engineering and screening workflows for rhizobia and non-rhizobia capable of expressing synthetic N₂ fixation genes. This work aims to enable the integration of biological nitrogen fixation capacity into cereal crops, thereby enhancing agricultural sustainability and crop productivity.He earned his integrated doctoral degree from Nagaoka University of Technology, Japan, where he was awarded the Japanese Government Scholarship. His doctoral research involved developing innovative high-throughput workflows for genetic modifications and strain improvements of the filamentous fungus Trichoderma reesei using a droplet-based microfluidic platform.

Collection Overview

Among legumes, two extensively studied mutualistic associations are those with rhizobia and arbuscular mycorrhizal (AM) fungi. These symbioses enhance nitrogen and phosphorus acquisition, thereby supporting sustainable agriculture and soil health. Such associations have been shown to improve legume growth and reduce fertilizer requirements. This collection presents reproducible, bench-ready protocols that emphasize practical, quantitative methodologies to advance research on these symbioses in both model and crop legumes.

The collection will include detailed protocols for the following:

Sterile symbiosis techniques, including optimized experimental conditions for newly domesticated or understudied legumes, standardized and multi-strain inoculation procedures, and co-cultivation with rhizobia and arbuscular mycorrhizal (AM) fungi
Molecular approaches to analyze symbiotic processes, such as the construction and application of fluorescent and luminescent bioreporters, as well as robust strategies for microbial strain labeling
Root clearing, staining, and sectioning procedures to visualize infection threads, nodules, and arbuscules
Functional assays to quantify nitrogen fixation, phosphorus uptake, and nutrient partitioning under controlled and semi-controlled experimental environments

Additional methods will include imaging workflows such as fluorescence and confocal microscopy, live-cell microscopy, omics pipelines, and computational tools for quantifying colonization, organ development, and overall symbiotic performance.

By integrating rigorous benchwork with robust analytical methods, this collection will provide a versatile toolbox suitable for laboratories with varying infrastructure capabilities. The protocols will emphasize stepwise reproducibility, troubleshooting guidance, and adaptability across legume species.