UNDERSTANDING THE MOLECULAR MECHANISM OF EMERGING INSECT RESISTANCE TO BT TOXIN CRY1F

Bt products are the major bioinsecticides used in agriculture and Bt-crops are widely adopted worldwide with proven economic and environmental benefits. However, development of Bt resistance in insect populations threatens the long-term future of Bt-biotechnology for insect pest management. Sustained application of Bt and Bt-biotechnology for insect pest control requires understanding the molecular mechanisms of Bt resistance in insects. The Bt toxin Cry1F is a major Bt toxin used in the current Bt-crops (cotton, maize and soybean varieties) and practical resistance to Cry1F-crops has occurred in four lepidopteran pests in the field. We have recently discovered and identified that high level resistance to Cry1F in the cabbage looper, Trichoplusia ni, is conferred by two resistance mechanisms combined -- the ABCC2 mutation associated resistance to Cry1Ac (cross-resistant to Cry1F) and a Cry1F-specific resistance mechanism which is novel yet to be identified. Therefore, to understand Cry1F resistance in insects fully, it is essential to understand the mechanism for the Cry1F-specific resistance. In this project, we aim to identify the novel resistance gene and the mutation conferring Cry1F-specific resistance in T. ni. To reach this research aim, we will use a genetic mapping approach combined with complementary OMICS techniques to map and identify the Cry1F resistance gene and mutation, and then use molecular and gene editing approaches to functionally validate the resistance gene and the mutation identified. Specifically, the objectives of this project are: (1) to identify the novel gene and mutation associated with the resistance to Cry1F in T. ni, to answer the question "What gene mutation is genetically associated with the Cry1F-specific resistance in T. ni?"; (2) to identify the change of midgut proteins and expression of midgut protein genes associated with the resistance to Cry1F in T. ni, to answer the question "What candidate midgut proteins are changed and their expressions are altered to potentially confer the resistance to Cry1F in T. ni?"; and (3) to functionally examine the resistance gene and mutation conferring the Cry1F resistance in T. ni, to answer the question "Specifically, what gene mutation functionally confers the Cry1F-specific resistance in T. ni?".