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This project seeks to create an on-demand "plant vaccine" which will help protect crops when diseased plants are detected nearby. To achieve this, we will use a non-infectious plant virus nanoparticle derived from tobacco mild green mosaic virus. This carrier has been successfully demonstrated in several agricultural applications approved by the USDA and EPA. The virus nanoparticle will be equipped with mRNA to stimulate an immune response in the plants and put them in a self-protective state. Specifically, we hope to stimulate the systemic acquired resistance pathway, which is found across many types of plants and gives long-term and broad-reaching immune protection to the plant. In many ways, the approach is similar to that of the COVID-19 mRNA vaccines, but adapted for plants and their immune systems. If successful, the technology developed in the project will serve as an environmentally friendly and biodegradable nanoparticle that can be directly applied to plants as a pre-exposure prophylactic when disease is detected in the field. This will help to reduce the environmental impact of pesticide application, will mitigate the persistence of unwanted chemicals in the soil and groundwater, and will serve as an effective strategy to protect valuable crops. This will lead to a more sustainable, economically viable, and health-focused approach to crop protection than some of the current methods. The project will also uncover some fundamentals about using protein-based nanocarriers for delivering a temporary change in the cells of plants. This work will also uncover new details about stimulating the systemic acquired resistance pathway and how effective this induction can be in preventing plant disease.Plant viruses are naturally designed to enter plant cells and deliver mRNA, making them an ideal carrier for the immune-stimulating transcripts. By decorating the exterior of these viruses with cell-penetrating peptides, we hope to increase how effective these carriers are at entering the cells and delivering their cargo. To ensure the system works, we will first load the mRNA for a green fluorescent protein into the viral nanoparticles. If successfully delivered, this transcript should direct the cells to produce a green fluorescent signal. The objectives of the project are as follows:1) We will test the system in a liquid culture of plant cells first to see how toxic the viral nanoparticles are when they deliver their cargo. We will use fluorescent microscopy and cell-viability assays to determine the effectiveness and safety of this approach.2) Once confirmed, we will advance to using a variety of whole plants at several stages of development, seeing which tissues express green fluorescence, the timescales to see this fluorescence, and how the health of the plants changes with the treatment.3) Once all the relevant information from green fluorescent expression has been determined, we will introduce candidate sequences of mRNA to turn on the systemic acquired resistance pathway and see which sequences protect the plants from an immune challenge such as introduction of bacteria or fungi.

Caparco, A. A.
University of California - San Diego
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