The CUP-SHAPED COTYLEDON1 gene of Arabidopsis regulates shoot apical meristem formation

In higher plants, molecular mechanisms regulating shoot apical meristem (SA M) formation and organ separation are largely unknown. The CUC1 (CUP-SHAPED COTYLEDON1) and CUC2 are functionally redundant genes that are involved in these processes. We cloned the CUC1 gene by a map-based approach, and foun d that it encodes a NAC-domain protein highly homologous to CUC2. CUC1 mRNA was detected in the presumptive SAM during embryogenesis, and at the bound aries between floral organ primordia, Surprisingly, overexpression of CUC1 was sufficient to induce adventitious shoots on the adaxial surface of coty ledons. Expression analyses in the overexpressor and in loss-of-function mu tants suggest that CUC1 acts upstream of the SHOOT MERISTEMLESS gene.