Elucidating the mechanism of baculovirus resistance (type I) in codling moth by identification of PE38-binding complex during the CpGV infection in Cp14R cells

• Applicant: Dr. Jiangbin Fan
• Subject Area: Plant Breeding and Plant Pathology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 491241735

The larvae of codling moth (CM, Cydia pomonella, family Tortricidae), called the “worm in the apple”, bore into unripe apples and complete their development inside, resulting in non-marketable fruits and high economic losses. Different Cydia pomonella granulovirus (CpGV) products, including resistance-breaking CpGV isolates, are being used to reduce infestation and avoid fruit damage caused by susceptible and resistant CM populations in pome fruit production in both organic and integrated pest management (IPM) plantations. Recently, the phenomenon of CpGV resistance to CM has been verified in seven European countries and in Washington State (USA); three types of resistance (type I - III) have been identified. Type I resistance is most widely distributed in European CM populations. It is targeted against the early transcribed viral gene pe38. CpGV isolates lacking a 2×12 bp repeat insertion in pe38 were shown to break type I resistance, promoting the development of resistance-breaking CpGV products and more sophisticated resistance management strategies. The present project will focus on the elucidation of the early events in CpGV infection process in CM. Preliminary work indicated that pe38 expression level is rather low in CpGV infection process of CM larvae or the CM Cp14R cell line, making it difficult to purify and identify the PE38 protein and its interacting protein/DNA. To resolve this limitation and to study the role of pe38 in CpGV infection and in the resistance process of CM larvae, stably transformed Cp14R-pe38 cell lines, constitutively expressing PE38, will be developed as a tool to further explore the function of PE38 and its targeted protein/DNA. LC-MS/MS and Illumina sequencing are applied to determine the sequence of amino acid derived from PE38 protein interaction complex and/or anchored nucleotide sequences, respectively. The available sequences and annotations of the CM genome and CpGV-M are in favour to localize the position of PE38-targeted gene/sequence in either host chromosome or viral genome. The location and movement of PE38 are traced during infection to screen the (dis)similarity between endogenous and exogenous PE38 using confocal fluorescence microscopy to determine where PE38 impacts on the virus infection. Transcription of selected viral genes is quantitated to measure the ability of different origins of PE38 that is in favour of virus replication and propagation in CpGV infection. The final outcome can answer the basic question how the CM blocks CpGV replication in early stage of infection and how to reduce/eliminate type I resistance and other resistance types by disrupting this infection pathway. Elucidating the function of pe38 can not only figure out the molecular mechanism of CpGV resistance, but will also point out the way for sustainable baculovirus formulations used in biological control.

• DFG Programme: Research Grants