Nitric oxide (NO) functions as both a gaseous neurotransmitter in the brain and a key signaling molecule in the innate immune system. NO is synthesized from arginine by the enzyme nitric oxide synthase (NOS). Our goal in this project was to utilize the house cricket Acheta domesticus to study the role of NO in both immune function and social behavior. Increasing NO levels in the brain causes male crickets to flee from other males (Stevenson and Rillich, 2016) and NO is released by insect immune cells during an inflammatory response (Foley and O’Farrell, 2003). During a previous study in our lab, we found that activation of the immune system with bacterial LPS caused male crickets to lose their fights with other males and to become socially subordinate. We hypothesized that NO released by immune cells during the inflammatory response was responsible for this loser effect. To test this, we first identified, cloned and sequenced the A. domesticus NOS gene from the cricket transcriptome. We then used the technique of systemic RNA interference (RNAi) to knockdown (KD), or reduce, expression of this gene. RNAi of the NOS gene will result in less NOS and, as a result, less NO produced by immune cells and brain cells. We report that RNAi of the NOS gene did, in fact, lead to a 60% reduction in NOS levels in the brain. Our next step will be to perform various immune assays in NOS KD male crickets. We will also determine if NOS KD alters the social behavior of these males. We also want to determine if injection of LPS into control males can lead to increased NOS expression and NO production in the brain. This would support our hypothesis that NO does, in fact, link inflammation to social subordinance. This experience has been relevant for my future career considering I intend to pursue further research and education in biology and neuroscience. The lab utilized several molecular techniques that have honed my scientific skills.
References:
Foley, E. and O’Farrell, P. H. (2003) Nitric oxide contributes to induction of innate immune responses to gram-negative bacteria in Drosophila. Genes and Development. 17(1), 115–25.
Stevenson, P. A. and Rillich, J. (2016) Controlling the decision to fight or flee: The roles of biogenic amines and nitric oxide in the cricket. Current Zoology. 62(3), 265–275.
Authors: Alexa Enders and Lauren Schaffer
Faculty Advisors: Kathleen Killian and Siva A. Lakshamana Vijayarajan, Department of Biology
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