Ever wonder why store-bought strawberries seem massive compared to the ones that you find in the wild? Or how some orchids sold at your local grocery store have flowers that stand out as giants among the rest?
Well, in these cases, what causes some plants to achieve their monstrous sizes is polyploidy or whole genome duplication. You may remember that humans are diploid, meaning they have two sets of chromosomes, one from mom and one from dad (di = two, ploid = sets of chromosomes), and the vast majority of other animal species are diploid as well. Between 30 and 80% of all plant species, on the other hand, can have diploid or polyploid varieties1 with 3, 4, 5 etc. sets of chromosomes. For instance, one genetic variety of the Dancing Crane Cobra Lily (Arisaema heterophyllum)2 has as many as 14 sets of chromosomes, making it a decatettaraploid! Because polyploid cells hold more genetic material than diploid ones, they are often larger, leading to monster-sized organisms. Humans have taken advantage of these size differences for centuries3 to grow larger produce to eat (hence the store-bought strawberries which are actually octoploid) and flowers to ornament our homes (those large-flowered orchids are probably tetraploid4).
Although humans have long used polyploid plants to grow more attractive crops, there are still many unanswered questions about why plants naturally evolve to be polyploid in the first place. My colleagues in the Ashman lab, Dr. Thomas Anneberg and Dr. Nathalia Streher, are addressing these key questions with their research. Specifically, Thomas is using laboratory and greenhouse studies to understand ecological polyploid establishment in the face of competition, and Nathalia is using herbarium records to uncover how polyploidy has affected pollination over time. Recently, I had the opportunity to collaborate with Thomas and Nathalia for the “Hopeful Monsters: Studying Polyploidy” display at the Carnegie Museum of Science during the “Plants and Botany Sci-Tech Days” event. Although my research is unrelated to polyploidy, Thomas and Nathalia helped me learn about this exciting field of study and pass on knowledge to the museum visitors. Using techniques I shared on my previous blog post (Tabling at Science Engagement Week), we engaged with people who visited our table by using many interactive examples of polyploid plants. These examples helped to teach what polyploidy is and how ubiquitous it is in the plant world and everyday life. We called polyploid plants “hopeful monsters” because of their size, of course, and also because of the uncertainty surrounding whether they will evolve and/or persist in certain natural environments.
One of the greatest aspects of being part of a research lab is being able to interact with and learn from fascinating researchers like Thomas and Nathalia. I had a blast at SciTech days and felt that the experience helped me gain a new appreciation of the influence of polyploidy in biology, just as many of the school kids who visited our table did as well.
So the next time you gawk at a humongous fruit or flower, consider that polyploidy may have played a role in the making of that monster.
Hopeful monsters display at Sci-Tech days! Our table included many familiar polyploid plants that we frequently eat and interact with such as strawberries, bananas, peanuts, seedless watermelons, blackberries, yams, ferns, orchids, and hibiscus. From left to right: myself, Dr. Thomas Anneberg, Dr. Nathalia Streher, Jae Kerstetter, and Trapper Hobble. Kerstetter and Hobble are fellow University of Pittsburgh researchers from the Turcotte lab who also ran a display about their research.
1Otto, S. P., & Whitton, J. (2003). POLYPLOID INCIDENCE AND EVOLUTION. 34, 401-437. https://doi.org/10.1146/ANNUREV.GENET.34.1.401
2Hayase, Y., Himeno, R., Horii, Y., & Iwatsubo, Y. (2019). Tetradecaploid cytotype of Arisaema heterophyllum (Araceae), newly found in Japan. Journal of Japanese Botany, 94(1), 9–14.
3Grlesbach, R. J. (1985). Polyploidy in Phalaenopsis orchid improvement. The Journal of Heredity, 76, 74–75.
4Salman-Minkov, A., Sabath, N., & Mayrose, I. (2016). Whole-genome duplication as a key factor in crop domestication. Nature Plants 2016 2:8, 2(8), 1–4. https://doi.org/10.1038/nplants.2016.115