Coi Receptors in Maize: Beyond Jasmonic Acid Perception

Jasmonic acid (JA) is a lipid-based phytohormone that plays an important role in plant defense. It is released in response to tissue wounding and induces plants to undergo specific transcriptional changes that protect them from herbivores. JA induction leads to the production of secondary metabolites that aid plants in fighting invasion and the release of volatile substances that attract parasitoids. In Arabidopsis, JA is known to be perceived by a protein called Coi1 (Coronatine Insensitive 1). In maize (Zea mays), however, evolutionary gene duplications have resulted in the presence of at least four Coi genes: Coi1a, Coi1b1, Coi1b2, and Coi2. These genes are either evolutionarily conserved, or have undergone neofunctionalization to detect other signaling molecules. The scientific community has yet to determine which combination of Coi1 proteins are the true receptors of JA, and if any of the Coi proteins are responsible for perceiving other distinct ligands.

In this experiment, we exposed single mutants of maize (Coi transposon insertion mutants) to caterpillar feeding and observed a potential difference in caterpillar weight, which would give us insight into JA perception, and potentially be indicative of another defense pathway. We first genotyped each plant by DNA extraction, amplification with polymerase chain reaction (PRC), and gel electrophoresis. In our bioassays we subjected plants that were homozygous mutant or wild type to feeding by fall armyworms (Spodoptera frugiperda), and made progress toward creating an efficient method of data collection. We also extracted RNA from five of the plants that we genotyped to be homozygous and performed reverse transcription to make cDNA, which will serve as proof that the mutant plants are incapable of expressing the Coi gene.

The future objectives of this project are replication of the bioassay to ensure the accuracy of results, as well as follow-up experiments using Coi double mutants, and later triple mutants.

My Experience

Through the BTI internship, I have been able to apply the knowledge gained in school to a real-life laboratory setting. By working alongside motivated scientists, I was able to learn new skills and methods, such as polymerase chain reaction (PCR), DNA extraction, and reverse transcription. I also acquired an in-depth understanding about my project. Not only did this experience teach me scientific techniques, but it also allowed me to work on my scientific fluency and oratory skills. The weekly seminars, lab meetings, and scientific papers read enhanced my ability to understand scientific content, and the poster presentation at the end of the internship allowed me to practice conveying my thoughts in an articulate manner. This experience has allowed me to think about my future in science; I have been inspired to pursue a biology related field.