Figure 1.

Models of phenotypic regulation by miRNA. (A) “Simple regulation”: A miRNA represses one target gene to control a phenotype. Different targets are responsible for different phenotypes. Red (blunt-headed) arrow indicates repression. (B) “Coordinated regulation”: A miRNA represses multiple targets, which in turn govern the same phenotype in the same direction. Pleiotropy, where a single target (e.g., Y₂) influences more than one phenotype, is common. (C) In the “redundant and incoherent regulation” model, a miRNA affects each phenotype through multiple targets redundantly and often incoherently. Pleiotropy is also common.