THE NO APICAL MERISTEM GENE OF PETUNIA IS REQUIRED FOR PATTERN-FORMATION IN EMBRYOS AND FLOWERS AND IS EXPRESSED AT MERISTEM AND PRIMORDIA BOUNDARIES

Petunia embryos carrying the no epical meristem (nam) mutation fail to develop a shoot apical meristem. Occasional shoots on nam(-) seedling s bear flowers that develop ten instead of five primordia in the secon d whorl. Double mutants with the homeotic gene green petals show that nam acts independently of organ identity in whorl 2 and now also affec ts primordium number in whorl 3. The nam gene was isolated by transpos on tagging. The encoded protein shares a conserved N-terminal domain w ith several other proteins of unknown function and thus represents a n ovel class of proteins. Strikingly, nam mRNA accumulates in cells at t he boundaries of meristems and primordia. These data indicate a role f or nam in determining positions of meristems and primordia.