Taking the stage: effectors in the spotlight

•Plant pathogens deploy host-translocated effectors to promote disease.•Hundreds of putative effectors have been identified, but few have been studied.•Knowledge of host targets, and/or effector activity, allows insight into function.•Understanding effector function offers opportunities for improving agriculture. Plant pathogens are a serious threat to agriculture and to global food security, causing diverse crop diseases which lead to extensive annual yield losses. Production of effector proteins by pathogens, to manipulate host cellular processes, is central to their success. An understanding of fundamental effector biology is key to addressing the threat posed by these pathogens. Recent advances in ‘omics’ technologies have facilitated high-throughput identification of putative effector proteins, while evolving cellular, structural and biochemical approaches have assisted in characterising their function. Furthermore, structures of effectors in complex with host factors now provide opportunities for applying our knowledge of effector biology to influence disease outcomes. In this review, we highlight recent advances in the field and suggest avenues for future research.