Insights intoPhakopsora pachyrhizieffector-effector interactions

The multifaceted role of pathogen-encoded effectors in plant-pathogen interactions is complex and not fully understood. Effectors operate within intricate host environments, interacting with host proteins and other effectors to modulate virulence. The complex interplay between effectors raises the concept of metaeffectors, where some effectors regulate the activity of others. While previous research has demonstrated the importance of effector repertoires in pathogen virulence, only a limited number of studies have investigated the interactions between these effectors. This study explores the interactions among Phakopsora pachyrhizi effector candidates ( Pp ECs). P. pachyrhizi haustorial transcriptome analysis identified a collection of predicted Pp ECs. Among these, Pp EC23 was found to interact with Pp EC48, prompting further exploration into their potential interaction with other effectors. Here, we utilized a yeast-two-hybrid screen to explore protein-protein interactions between Pp ECs. A split-luciferase complementation assay also demonstrated that these interactions could occur within soybean cells. Interestingly, Pp EC48 displayed the ability to interact with several small cysteine-rich proteins (SCRP), suggesting its affinity for this specific class of effectors. We show that these interactions involve a histidine-rich domain within Pp EC48, emphasizing the significance of structural motifs in mediating effector interactions. The unique nature of Pp EC48, showing no sequence matches in other organisms, suggests its relatively recent evolution and potential orphan gene status. Our work reveals insights into the intricate network of interactions among P. pachyrhizi effector-effector interactions.