The spruce bark beetle (Ips typographus) has caused great economic and ecological losses in Norwegian spruce forests. Warming temperatures are predicted to cause an increase in the frequency of bark beetle attacks. Recent work has shown that treating spruce trees with a naturally produced tree hormone, methyl jasmonate, helps the trees defend themselves against spruce bark beetle attacks. This treatment is similar to a person getting a vaccination. When painted with methyl jasmonate, a tree builds up defenses which can be rapidly deployed when the tree is under attack. This initial increase in ability to respond to attack can last for weeks or months. In this project, we are seeking to understand the changes that occur at the cellular and molecular level to make possible this rapid response. In addition, methyl jasmonate treatment produces new "memories" for the tree. These "memories" are stored as changes to the tree's DNA and allow the tree to continue to have heightened defense responses for months or even years. This process is called "defense priming". In this project, we will explore how these DNA "memories" are made. We are also interested to see if these "memories" can be passed on to the offspring of treated trees. If so, we may be able to help protect the next generation of forests from increased bark beetle attack by immunizing their parents with methyl jasmonate. So far we have learned that increasing ability to produce enzymes that breakdown fungal cell walls is one of the important memories stored after methyl jasmonate treatment.