Research

Publications:

For more information, check out my Google Scholar profile.

Yoshida, S., Kim, S., Wafula, E.K., Tanskanen, J., Kim, Y.-M., Honaas, L., Yang, Z., Spallek, T., Conn, C.E., Ichihashi, Y., Cheong, K., Cui, S., Der, J.P., Gundlach, H., Jiao, Y., Hori, C., Ishida, J.K., Kasahara, H., Kiba, T., Kim, M.-S., Koo, N., Laohavisit, A., Lee, Y.-H., Lumba, S., McCourt, P., Mortimer, J.C., Mutuku, J. M., Nomura, T., Sasaki-Sekimoto, Y., Seto, Y., Wang, Y., Wakatake, T., Sakakibara, H., Demura, T., Yamaguchi, S., Yoneyama, K., Manabe, R., Nelson, D.C., Schulman, A., Timko, M.P., DePamphilis, C.W., Choi, D., Shirasu, K. (2019) Genome sequence of Striga asiatica provides insight into the evolution of plant parasitism. Current Biology 29(18): 3041 – 3052. e4.

Conn, C.E., Nelson, D.C. (2017) It’s not easy being not green: the making of a parasitic plant. The Plant Cell 29(4): tpc.117.tt0417; DOI 10.1105/tpc.117.tt0417.

Lopez-Obando, M., Conn, C.E., Hoffmann, B., Bythell-Douglas, R., Nelson, D.C., Rameau, C., Bonhomme, S. (2016) Structural modeling and transcriptional responses highlight a clade of PpKAI2-LIKE genes as candidate receptors for strigolactones in Physcomitrella patens. Planta DOI 10.1007/s00425-016-2481-y.

Conn, C.E., Nelson, D.C. (2016) Evidence that KARRIKIN-INSENSITIVE2 (KAI2) receptors may perceive an unknown signal that is not karrikin or strigolactone. Frontiers in Plant Science 6:1219. DOI 10.3389/fpls.2015. 01219.

Conn, C.E., Bythell-Douglas, R., Neumann, D., Yoshida, S., Whittington, B., Westwood, J.H., Shirasu, K., Bond, C.S., Dyer, K.A., Nelson, D.C. (2015) Convergent evolution of strigolactone perception enabled host detection in parasitic plants. Science 349(6247): 540 – 543.

Hedges, S.B., Conn, C.E. (2012) A new skink fauna from Caribbean islands (Squamata, Mabuyidae, Mabuyinae). Zootaxa 3288: 1 – 244.

Overview

Symbiotic relationships can take different forms, including mutualism, commensalism, and parasitism (although these categories are not as discrete as they’re often considered to be!). I focus on parasites, and I’m broadly interested in the genetic basis of their detection and utilization of a host. Specifically, my research in genetics addresses the following three questions about how parasites interact with hosts:

• How do parasites perceive hosts?
• What determines host range and preference in parasites?
• How can resistance to parasites be improved in susceptible host species?

I address these questions in parasitic plants from the Orobanchaceae and in American chestnut trees. Berry College sits on 27,000 acres, and several species of Orobanchaceae are found right here on campus! Professor Marty Cipollini has also established an impressive chestnut breeding program here, with multiple orchards on campus. In my research, I aim to engage undergraduates in field collection, laboratory experiments, and bioinformatics to address important questions about how parasites and hosts interact.

In the past, I’ve worked in animal and plant systems. More information on specific projects is below.

Parasites of ant agriculture (National Science Foundation Postdoctoral Research Fellowship in Biology at Emory University)

Leafcutter ants are fascinating to watch as they form long lines and carry plant material through forests and into their colonies. But what are they doing with the leaves they harvest? Leafcutters and their relatives are some of the world’s oldest farmers; they cultivate mutualistic fungi inside their colonies, which they feed with cut leaves or other material. Another fungus called Escovopsis parasitizes the ants’ cultivars, which the ants combat by “weeding out” infected pieces of their garden and by associating with bacteria that product pathogen-suppressing compounds. Despite the ants’ defenses, Escovopsis infestation sometimes leads to ant colony collapse.

The ants, their fungal cultivars, and Escovopsis have a tight coevolutionary history. Escovopsis usually has high host specificity and parasitizes cultivars with which it can be found in nature. However, a major host-switching event by Escovopsis has been documented in the evolutionary history of this system. My work addressed questions about the genomic features and transcriptomic responses that underlie that host switch. I also investigated finer-scale host specificity in Escovopsis, which is a project I  incorporated into a course-based undergraduate research experience at Spelman College.

Mentor at Emory University: Dr. Nicole Gerardo

Blood-feeding parasites of songbirds (CURE Postdoctoral Fellowship, Spelman College)

When we think of blood feeding parasites, we often picture mosquitoes, ticks, and other pests that affect us as humans. A littler-known blood feeder that parasitizes bluebirds and tree swallows is a blowfly in the genus Protocalliphora. Protocalliphora is related to mosquitoes but evolved blood feeding independently. Furthermore, while mosquitoes feed on blood as adults, Protocalliphora are only parasitic as larvae. These differences between the two parasites facilitate a comparative transcriptomics analysis of how blood feeding evolves. At Spelman, I worked closely with an undergraduate researcher to address this question. I also investigated whether horizontal gene transfer – the transfer of genetic material laterally from one species to another rather than vertically from parents to offspring – has occurred in Protocalliphora. As a current side project, I hope to examine the transcriptomic basis of host preference in Protocalliphora.

Mentor at Spelman College: Dr. Jennifer Kovacs

Plant parasites of major crops (Dissertation, National Science Graduate Research Fellowship at the University of Georgia)

Did you know that plants can be parasites, too? Parasitic plants are diverse, destructive, and more common than we might realize! The definition of a parasitic plant is somewhat contentious; some people consider “true parasites” to be those that directly connect to a host plant, while others include plants that steal from other plants via a fungal intermediate. The parasitic plants that I study (family: Orobanchaceae) connect to the roots or shoots of host plants with a specialized invasive structure called a haustorium. Many parasitic plants in this family use important crops as hosts, such as rice, maize, tomatoes, tobacco, sunflowers, carrots, and legumes. They cause tremendous damage to agriculture in various parts of the world, and they’re difficult to control for a number of reasons. One is that the tiny parasite seeds remain dormant in the soil until they detect a nearby host. Then they germinate, grow toward their soon-to-be host, and damage it before becoming visible above the soil surface. My dissertation work addressed the question of how parasite seeds detect hosts and germinate in response. After identifying the genes that contribute this adaptation in parasitic plants, I investigated what similar genes do in parasites and in non-parasitic relatives. Figuring out how these parasites take the first step towards attacking crop plants was an exciting discovery for my research group, and I hope my work will help with the development of more effective control strategies for parasitic plants in agricultural settings.

Mentor at the University of Georgia: Dr. David Nelson