Functional role of the Myzus persicae (Green Peach Aphid) effector repertoire in host plant manipulation.

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Aphids are sap-feeding insects that induce extensive feeding damage, achieve high population densities and transmit economically important plant diseases worldwide. These insects cause significant economic losses in staple food and bioenergy crops, including potato, soybean, cereals, and oilseed rape. Aphid infestations are expected to increase in the future as a result of environmental changes and increased restrictions on the use of pesticides. To develop durable approaches and achieve sustainable control of aphid epidemics, it is critical to understand aphid parasitism at the molecular level. Key questions herein are: What proteins do aphids deliver inside host plants to enable infestation? How do aphids affect host cell processes? Can we generate crop varieties that have durable resistance to aphids, and thereby reduce dependence on pesticides? Like most plant parasites, aphids require intimate associations with their hosts to gain access to nutrients. Aphids have specialized mouthparts, stylets, which they use to probe different plant cell types, and to feed on plant sap in the plant vascular system. Interestingly, aphid feeding induces clogging of phloem sieve elements in the plant vascular system, which is suppressed by aphids in successful host interactions. Furthermore, aphids can perturb plant developmental processes by, for example, inducing leaf curling or the formation of galls. Suppression of plant defences and altering host physiology is common among plant pathogens and generally involves the secretion of pathogen molecules, or effectors, into host plants that manipulate plant cellular processes. This manipulation of plant cell processes may involve suppression of host defences as well as altering plant cellular processes to promote the release of nutrients through targeting of specific plant (defence) proteins. Recent evidence suggests that aphids, like other plant parasites, secrete effectors that share functional features with plant pathogen effectors. Among the over 5000 aphid species, Myzus persicae (green peach aphid) is one of the most destructive pests worldwide, partly due to its broad host range that spans hundreds of different plant species. This host range includes important crop plants, including potato, as well as model plants Nicotiana benthamiana and Arabidopsis thaliana for which an extensive set of experimental tools and resources are available. In this project, we aim to identify effectors from the aphid species M. persicae and characterize their role in plant infestation. More specifically, we will perform functional assays in N. benthamiana plants to identify novel (candidate) M. persicae effectors. To investigate the role of aphid effectors in plant cell manipulation, we will identify the plant proteins in N. benthamiana and potato that are directly targeted, and potentially modified, by M. persicae effectors. Also, we will determine the contribution of identified M. persicae effector plant targets to plant infestation. The expected results of this project will allow a comprehensive view of the strategies that aphids employ to infest plants. Specifically, this work will implicate plant and insect proteins in an economically important interaction. An understanding of the plant cellular processes targeted by aphids and the effectors required for parasitism will facilitate the development of novel and sustainable aphid control strategies to increase crop yield and reduce pesticide usage.