Abstract
The shoot apical meristem is characterized by the expression of KNOX1 genes. KNOX1 genes have been implicated in the acquisition and/or maintenance of meristematic fate. One of the earliest indicators of a switch from indeterminate meristem to determinate leaf primordium is the down-regulation of KNOX1 genes orthologous to SHOOT MERISTEMLESS (STM) in the initiating primordia. In simple-leafed plants, this down-regulation persists during leaf formation. In compound-leafed plants, however, the expression is later re-established in the developing primordia, creating an indeterminate environment for leaflet formation.
Here we identify two conserved sequences within the 5' upstream region of STM genes in both simple- and compound-leafed species across monocots and dicots. We show that one of them is involved in the regulation of the persistent repression and/or the re-establishment of STM expression in the developing leaves but not the initial down-regulation. We also show that this regulation is significant for leaf develpment.
