Myzus persicae secretes an auxin-synthesizing enzyme while feeding

The green peach aphid (Myzus persicae) is a generalist herbivore, feeding on a variety of species in several different plant families. Many of these plants are valuable agricultural crops such as cabbage, potato, tomato, and corn. Investigating the feeding mechanisms of M. persicae, and the effects of herbivory on plants is vital to developing aphid-resistant crops. In previous research, auxin biosynthesis from tryptophan was identified through LC-MS of aphid-fed artificial diet. Other studies indicated increased expression of DAO1, the gene encoding the enzyme DIOXYGENASE FOR AUXIN OXIDATION 1 (DAO1) in Arabidopsis thaliana (Arabidopsis), 48 hours after the start of aphid feeding. It is hypothesized that whilst aphids are secreting an auxin-synthesizing enzyme, plants respond to aphid feeding by upregulating the expression of DAO1. Utilizing mutant and transgenic Arabidopsis lines (DR5:GUS and dao1 DR5:GUS), we aimed to visualize increased levels of auxin at the aphid feeding site through GUS staining. Results of GUS staining were inconclusive. Interestingly, aphid-fed dao1 DR5:GUS Arabidopsis leaves did not show more GUS activity than aphid-fed DR5:GUS Arabidopsis leaves. Although further replications of this study are needed, these results may suggest the upregulation of auxin inactivation through a mechanism other than DAO1. Further investigation into mechanisms of auxin catabolism within dao1 Arabidopsis may help elucidate these results. In addition, 24-hour aphid choice assays with wildtype and dao1 Arabidopsis were performed to determine if M. persicae preferred feeding on Arabidopsis plants that were unable to oxidize auxin. Statistical analysis of aphid choice assays did not reveal any significant differences, which is distinct from prior no-choice assays where aphids produced more progeny on dao1 Arabidopsis.

Being a part of the REU program at the Boyce Thompson Institute has been an invaluable first research experience for me. In addition to learning new lab techniques and protocols, I gained insight into what a career in scientific research entails. The weekly seminars also allowed me to learn about various areas of plant biology and connect with passionate faculty and staff at BTI and Cornell. I was additionally able to participate in scientific outreach in the local community, which taught me how to effectively convey scientific research to the general public. I am especially grateful to my PI and mentor, Georg Jander, who never emphasized my mistakes and instead encouraged my learning. These past ten weeks have truly been unforgettable for me, and I will carry the skills I have learned here into each and every new step I take in the future.