Plant diseases constrain crop production, threaten global food security, and impact ecosystem health. Our research aims to elucidate the molecular mechanisms pathogenic fungi use to manipulate the host plant and cause disease. I will discuss our latest findings on an effector protein family utilised by diverse pathogenic fungi. This effector family belongs to an ancient enzyme superfamily called Nudix hydrolases. We have established that fungal Nudix effectors can be split into two evolutionary and functionally distinct groups. The first group is exclusive to rust fungi from the Melampsora genus and our results demonstrate that these enzymatic effectors specifically hydrolyse the protective 5′ cap structure on mRNA, likely altering plant mRNA decay dynamics and influencing gene expression. The second group of Nudix effectors are utilised by multiple economically important pathogenic fungi including Magnaporthe oryzae and Colletotrichum graminicola. In this presentation I will describe the molecular mechanism these effectors use to manipulate the highly conserved plant phosphate sensing pathway and exacerbate disease. Phosphate sensing is crucial for the regulation of symbiotic plant-fungal interactions, and therefore our research on the Nudix effectors provides direct evidence for the hijacking of symbiosis-facilitating mechanisms to promote disease.