Erika Calle

Date of Award

2023

Document Type

Thesis

Degree Name

Bachelors

Department

Natural Sciences

First Advisor

Diaz Almeyda, Erika

Area of Concentration

Natural Sciences

Abstract

This thesis investigated the roles of host-gut symbiotic interactions of Candidatus Ishikawella capsulate and Kudzu bugs in the Southeastern United States. Exploring the host-microbe interactions can provide insight into understanding the overall health of species. While the microbes get a habitat and nourishment from the host, these microbes, in turn, help the host by regulating various host physiological functions, including dietary digestion, and imparting protective immunity against pathogens (Khan et al.,2019). Megacopta cribraria or the Kudzu bug is an invasive species of stink bug from the Kyushu region of Japan that invaded the state of Georgia in 2009 (Eger et al., 2010). They are a formidable invasive species that has spread to more southeastern states (Gardner et al., 2013; Leslie et al., 2014; Ruberson et al., 2013 ). The Kudzu bug's excessive feeding behavior on the sap of soybean plants negatively impacts soybean yield by reducing pods per plant, reducing beans per pod, and possibly reducing seed size (Seiter et al., 2013). The Kudzu bug has a unique method of transmitting their gut symbionts to the next generation. Adult female Kudzu bugs create protein capsules that contain gut bacteria such as Gamma-proteobacteria Candidatus Ishikawella capsulata and deposit them alongside each egg mass (Kikuchi et al., 2007 and Hosokawa et al., 2008). Aposymbiotic nymphs ingest the gut bacteria present in the capsule (Hosokawa et al., 2008). This nature of acquiring gut symbionts has provided researchers a method to further conduct experiments to examine the nature of symbiont-host interactions by sterilizing the capsule via heat treatment (Takema Fukatsu & Hosokawa, 2002). Previous studies such as Couret. Et.al. 2019 and Geraldo et.al 2020 have indicated that Candidatus Ishikawella capsulata plays a big role in the developmental stages and the survival to adulthood. This thesis investigation involved examining a raw data google excel sheet belonging to a previous study conducted by Geraldo et.al lab. The one of the main focus was on caterogizing the upregulation and downregulation of immune -related genes present in the kudzu bugs’ dissected crypts of kudzu bugs that fed on soybean plants with and without Candidatus Ishikawella capsulata present. I coded in R-studio to make a list of all of the last GO terms listed in the immune- related genes data sheet. I used the list to map out the main functions of the genes using the REVIGO database to summarize and organize the last GO terms into an interactive functions map. The results indicate that Candidatus Ishikawella capsulata plays an important role in the overall health of Kudzu bugs. When examining the transcriptome of kudzu bugs without symbionts, the gene expression of response to starvation was highly expressed. Candidatus Ishikawella capsulate compensates for the shortage of essential amino acids in the diet by providing branched-chain amino acids and aromatic amino acids in which compliments and completes the host’s whole diet (Moriyama & Takema Fukatsu, 2022). The results show that the symbiont plays a potentially significant role in the immune system. The Revigo chart shows that the symbiont has a role to play in the regulation of the innate immune system and carrying out innate immune responses to bacterium. Without the symbiont, the regulation of the immune system is affected which means one can expect a decline in responses needed to successfully fight off pathogens. The results of this investigation provide additional supporting evidence for Candidatus Ishikawella capsulata being an obligate symbiont for Megacopta cribraria.

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