Mucilage Microbial Isolates 2.0: future directions for the corn project

Contributed by Shawn Higdon

In the summer of 2013, I joined the lab of Alan Bennett at U.C. Davis as a Junior Specialist with the Department of Plant Sciences. All I knew at that time is that I would be working on a research project with an isolated variety of corn from Mexico that had a very unusual phenotype. I soon discovered that the project was highly collaborative with multiple principle investigators on board, the project had already been going on for several years, and that the Weimer lab was working on the project to generate a collection of microbes that were isolated from this intriguing variety of corn. While my role in the project began as a technician processing dried tissue samples for elemental analysis by isotopic ratio mass spectrometry in a robot-like fashion, I had no idea of how much potential this project had to offer both me and the scientific community.

Fast-forward nearly five years to the present and I am now a graduate student in the Plant Biology Graduate Group at U.C. Davis working on a different facet of the same project. The tentative title of my Ph.D. dissertation project is, “Characterization of plant growth promoting functions from the maize aerial root microbiota.” The foundation of my project stems directly from the amazing work performed by the Weimer lab to generate a robust collection of microbial isolates from the aerial root mucilage of maize that grows naturally in the Sierra Juarez region of Mexico. Specifically, the variety of maize that we are working with exhibits the extended development of aerial roots that exude copious volumes of a polysaccharide-rich mucilage. Metagenomic analysis indicated that the mucilage environment supports a distinguished microbiota, and compositional analysis of the mucilage polysaccharide has also revealed that the host secrets a highly diverse complex-carbohydrate that may be the driving force behind associations with microbes that confer plant growth promotion or PGP.

The work that I have achieved so far during my pursuit of a Ph.D. has largely been centered around generating and analyzing whole genome sequence data from subsets of the microbes within the Weimer lab’s collection of maize microbial isolates. This work, while initially unanticipated, has changed my way of thinking and opened the door for me to an area of science that lies at the interface of Microbiology, Plant Biology, and Bioinformatics. I favor the classification of the research that I do within the area of sustainable agriculture, which is something that I am very passionate about being involved in both currently as a student and hopefully in the future. Given the context of the system I am working with, my time spent conducting research on this project, and the experiences that I have acquired thus far, I have developed the following hypotheses that I would like to test in some form during my Ph.D.:

1) mucilage polysaccharide derivatives are utilized by maize aerial root microbes for their own growth

2) mucilage polysaccharide derivatives are capable of sustaining modes of PGP conferred by maize aerial root microbes

3) members of the aerial root mucilage microbiota cooperate through metabolic specialization to confer PGP

4) microbial isolates are capable of utilizing their specialized functionalities to confer PGP upon other plant species (essentially challenging host specificity)

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