P-433 - Deciphering the Agrobacterium tumefaciens transcriptome landscape under in vivo conditions.

Agrobacterium spp. induce the formation of crown gall tumors by integrating their T-DNA into the plant genome. During integration agrobacteria make use of virulence proteins (effectors), either for T4SS assembly (VirD4, VirB), generate single stranded T-DNA (VirD, VirC), or protect T-DNA from degradation in the host cell (VirD2, VirE). Transcription of virulence genes is controlled by the VirG/VirA signalling complex, which perceives and responds to environmental cues including pH, sugars and plant derived factors. While the transcriptome of A. tumefaciens is well characterized under in vitro conditions, the interaction with the host plant in vivo has not been previously studied. To address this, we first investigated how bacterial growth conditions influence virulence gene expression. qRT-PCR analyses revealed how pH, sugars, and acetosyringone impact transcriptomic responses. Additionally, bacteria from different growth conditions were used in an Arabidopsis thaliana transient expression assay to assess in vivo virulence patterns. Next, we will isolate Agrobacterium directly from infected plants and perform transcriptomic analyses to uncover plant-driven bacterial responses. This study aims to differentiate host-induced gene expression from environmental influences, providing insights into Agrobacterium-plant interactions under natural infection conditions.