The roles of metals in insect-microbe interactions and immunity

Metal ions play essential roles in diverse physiological processes in insects, including immunity and interactions with microbes. Some, like iron, are essential nutrients and therefore are the subject of a tug-of-war between insects and microbes. Recent findings showed that the hypoferremic response mediated by Transferrin 1 is an essential defense mechanism against pathogens in insects. Transferrin 1 and the overall iron metabolism were also implicated in mediating interactions between insects and beneficial microbes. Other metals, like copper and zinc, can interfere with insect immune effectors, and either enhance (antimicrobial peptides) or reduce (reactive oxygen species) their activity. By covering recent advances in the field, this review emphasizes the importance of metals as essential mediators of insect-microbe interactions.