Agrobacterium is a captivating bacterial plant pathogen renowned for its ability to transfer genetic material into the plant genome. Humans harnessed this unique capability to create plants with desirable agronomic traits. Plant-pathogen interactions are typically determined by complex interaction networks involving both bacterial effectors and plant host proteins. While research on bacterial DNA transfer and integration has dominated the Agrobacterium field, there is a lack of knowledge on how effectors hijack plant defense responses. This is highlighted by the fact that for many plant species, notably monocots, genetic transformation remains challenging. To address this knowledge gap, we will utilize new techniques in proteomics, based on proximity-dependent labeling, to identify novel effector-host protein interactions within the host cellular environment. Concurrently, we will employ two high-end approaches to identify potential novel effectors. We will characterize proteins translocated by the secretion system within Agrobacterium and identify bacterial proteins in planta. Finally, we will functionally characterize novel host proteins in both maize and Arabidopsis and study the importance of both novel effectors and host proteins in infection. Our comprehensive approach will undoubtedly provide a deeper understanding of this intriguing natural interkingdom interaction and may lead to improvements in biotechnological applications.