Unraveling the enigma of ‘Candidatus Phytoplasma solani’

Grapevine production in Europe faces pressure from phytoplasma diseases, particularly from Candidatus Phytoplasma solani, the causal agent of the grapevine yellows disease Bois Noir. This pathogen leads to severe crop losses and currently lacks effective control strategies. To develop targeted and sustainable disease management approaches, a deeper understanding of the molecular interactions between the pathogen and host plants is needed. The project addresses the molecular mechanisms of Ca. P. solani infection, focusing on effector proteins, which are key molecules used by the pathogen to manipulate host cellular processes. The primary goal of the project is to elucidate how these effectors interact with plant transcription factors and signaling proteins (referred to as plant factors) in grapevine and the model plant Arabidopsis. To understand how these effectors function, the project will introduce selected bacterial proteins into Arabidopsis and into grapevines. By observing where the effectors go within plant cells and what changes they cause in plant growth and development, the specific roles in disease progression will be elucidated. Another major focus is identifying the host plant proteins - particularly transcription factors and signaling molecules - that interact with the pathogens effectors. Through RNA sequencing and data integration, the project will pinpoint which plant genes are activated or suppressed during infection. These findings will be followed by targeted laboratory experiments to confirm how these plant factors bind with effectors and what functional consequences arise from these interactions. The project also investigates how effector activity affects broader plant processes. By examining changes in gene expression and enzyme activity in plants transformed with effector genes, a detailed picture of how the pathogen reprograms the hosts metabolism and immune system will be generated. These insights are crucial for developing future-resistant plant lines or new treatment approaches. All data will be managed according to FAIR principles to ensure transparency, reusability, and accessibility for the global research community. With a strong collaboration among leading laboratories in Slovenia, Croatia, and Austria with a long-standing track record in phytoplasma research, the project is expected to deliver significant advances in our understanding of plant- pathogen interactions and open new paths for disease control in grapevine and other crops.