Nancy Holbrook is a recent graduate who majored in Biology. She was awarded a Fall 2016 Independent Grant which she used to conduct research on fascinating fungi in milkweed under Dr. Nicole Gerardo.
As an undergraduate researcher in the Gerardo lab, I am not only attracted to the monarch butterfly for its bold beauty. I, and the rest of the Gerardo lab, am also interested in exploring some very unique interactions that monarchs have with their environment. A particular parasite called Ophryocystis elektroschirra often infects monarch butterflies, but interestingly enough, the food source that a monarch chooses for its young can affect how resistant its offspring are to this parasite. Monarch butterflies lay their eggs on milkweed plants. Several different species of milkweed can be found in the wild, and research has shown that different milkweed species contain different levels of chemicals called cardenolides. Butterflies that feed on milkweeds with higher cardenolide levels tend to be less heavily infected with the parasite than butterflies who choose lower cardenolide milkweeds (1). Because differing species of milkweed plant seem to play such a big role in determining parasite disease resistance of monarchs, we are interested in understanding more about plant properties.
As an undergraduate researcher in the Gerardo lab, I am not only attracted to the monarch butterfly for its bold beauty. I, and the rest of the Gerardo lab, am also interested in exploring some very unique interactions that monarchs have with their environment. A particular parasite called Ophryocystis elektroschirra often infects monarch butterflies, but interestingly enough, the food source that a monarch chooses for its young can affect how resistant its offspring are to this parasite. Monarch butterflies lay their eggs on milkweed plants. Several different species of milkweed can be found in the wild, and research has shown that different milkweed species contain different levels of chemicals called cardenolides. Butterflies that feed on milkweeds with higher cardenolide levels tend to be less heavily infected with the parasite than butterflies who choose lower cardenolide milkweeds (1). Because differing species of milkweed plant seem to play such a big role in determining parasite disease resistance of monarchs, we are interested in understanding more about plant properties.
My project is focused on understanding the fungal endophyte communities inside two species of milkweed plant (Asclepias incarnata and Asclepias curassavica). First, what is a fungal endophyte? Fungal endophytes are really just fungi which live inside plant tissues, like leaves and roots (2). Relatively little research has been done on the importance and diversity of fungal endophytes, but existing studies have shown that some endophytes have ecological roles within the plants they inhabit. For example, fungal endophytes found in fescue grass have been found to enhance the plant’s growth in times of drought (3). Because we know that the milkweeds A. incarnata and A. curassavica have differing chemical compositions, we hypothesize that it is also possible that the two species contain different fungal endophyte communities. If the two milkweeds are found to contain different fungal endophytes, it is possible that these fungi may play some role in affecting how beneficial certain milkweed species are in preventing parasite infection in monarchs.
Research on the project began in early September. I am currently working on culturing (growing) fungal endophytes from many different leaf samples. I have run into some difficulty in growing fungal endophytes from my milkweeds. In early stages of plating the milkweed leaves, I was finding that very few milkweed samples contained endophytes. However, this could possibly be due to the fact that the milkweeds I sampled from had been grown as potted plants in a greenhouse environment at the top of a 7-story parking deck. Plants likely had less exposure to fungal spores in this environment than they would have had in a natural environment. I have since been able to locate older milkweeds in a few different natural environments (my PI’s home garden, the Carter Center, and the garden at Fernbank). The milkweeds that were sampled from these locations contained plenty of fungal endophytes, many of which were surprising colors and patterns! I have cultured quite a few fungi from A. incarnata plants and my next goal is to isolate more fungi from A. curassavica so that I will have sufficient data for comparison of fungal endophytes between the two species.
Above are two different fungal endophytes isolated from an A. incarnata milkweed cutting.
As more fungi are being isolated and grown from the plant material, I am creating a kind of living archive by stocking samples of the fungi in sterilized water so that the fungal strains can be revived and regrown later. In addition, samples of each strain are being collected for the next step of DNA analysis and determination of the species classification of each fungus. Through the countless hours spent sterilizing and plating plant tissue (sometimes to no avail!) I am definitely learning lots of patience, but being able to successfully culture endophytes and appreciate their beauty is also interesting and a lot of fun!
References:
(1) De Roode JC, Pederson AB, Hunter MD, Altizer S. 2008. Host plant species affects virulence in monarch butterfly parasites. Journal of Animal Ecology. 77:120-126.
(2) Arnold AE. 2007. Understanding the diversity of foliar endophytic fungi: progress, challenges, and frontiers. Fungal Biology Reviews. 21:51-66.
(3) Vinton MA, Kathol ES, Vogel AP, Hopkins AA. 2001. Endophytic fungi in Canada wild rye in natural grasslands. Journal of Range Management. 54:390-395.
Visit the Undergraduate Research Programs website to learn more about applying for Independent Research Grants.
Research on the project began in early September. I am currently working on culturing (growing) fungal endophytes from many different leaf samples. I have run into some difficulty in growing fungal endophytes from my milkweeds. In early stages of plating the milkweed leaves, I was finding that very few milkweed samples contained endophytes. However, this could possibly be due to the fact that the milkweeds I sampled from had been grown as potted plants in a greenhouse environment at the top of a 7-story parking deck. Plants likely had less exposure to fungal spores in this environment than they would have had in a natural environment. I have since been able to locate older milkweeds in a few different natural environments (my PI’s home garden, the Carter Center, and the garden at Fernbank). The milkweeds that were sampled from these locations contained plenty of fungal endophytes, many of which were surprising colors and patterns! I have cultured quite a few fungi from A. incarnata plants and my next goal is to isolate more fungi from A. curassavica so that I will have sufficient data for comparison of fungal endophytes between the two species.
As more fungi are being isolated and grown from the plant material, I am creating a kind of living archive by stocking samples of the fungi in sterilized water so that the fungal strains can be revived and regrown later. In addition, samples of each strain are being collected for the next step of DNA analysis and determination of the species classification of each fungus. Through the countless hours spent sterilizing and plating plant tissue (sometimes to no avail!) I am definitely learning lots of patience, but being able to successfully culture endophytes and appreciate their beauty is also interesting and a lot of fun!
References:
(1) De Roode JC, Pederson AB, Hunter MD, Altizer S. 2008. Host plant species affects virulence in monarch butterfly parasites. Journal of Animal Ecology. 77:120-126.
(2) Arnold AE. 2007. Understanding the diversity of foliar endophytic fungi: progress, challenges, and frontiers. Fungal Biology Reviews. 21:51-66.
(3) Vinton MA, Kathol ES, Vogel AP, Hopkins AA. 2001. Endophytic fungi in Canada wild rye in natural grasslands. Journal of Range Management. 54:390-395.
Visit the Undergraduate Research Programs website to learn more about applying for Independent Research Grants.
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