Role for the shoot apical meristem in the specification of juvenile leaf identity in Arabidopsis

Significance Developmental transitions during shoot development in plants are regulated by factors originating outside and within the shoot apical meristem (SAM). The best-known example of this is the vegetative-to-reproductive transition, which is initiated by a leaf-derived signal that transforms the vegetative SAM into a developmentally stable inflorescence meristem. Although the juvenile-to-adult vegetative transition (vegetative phase change) is also thought to be regulated by factors exogenous and internal to the SAM, how this process is coordinated spatially remains unknown. Here we demonstrate that the SAM specifies leaf identity early in development, but that leaves become more important determinants of shoot identity as the shoot ages. We also reveal a role for the plant aging pathway in the regulation of meristem size.