THE CURLY LEAF GENE CONTROLS BOTH DIVISION AND ELONGATION OF CELLS DURING THE EXPANSION OF THE LEAF BLADE IN ARABIDOPSIS-THALIANA

The CURLY LEAF (CLF) gene in Arabidopsis thaliana (L.) Heynh. is requi red for stable repression of a floral homeotic gene, AGAMOUS in leaves and stems To clarify the function of CLF in organ development, we cha racterized clf mutants using an anatomical and genetic approach. The e lf mutants had normal roots, hypocotyls, and cotyledons, but the folia ge leaves and the stems had reduced dimensions. A decrease both in the extent of cell elongation and in the number of cells was evident in t he clf mutant leaves, suggesting that the CLF gene might be involved i n the division and elongation of cells during leaf morphogenesis. An a nalysis of the development of clf mutant leaves revealed that the peri od during which cell division or cell elongation occurred was of norma l duration, while the rates of both cell production and cell elongatio n were lower than in the wild type. Two phases in the elongation of ce lls were also recognized from this analysis. From analysis of an angus tifolia elf double mutant, we found that the two phases of elongation of leaf cells were regulated independently by each gene. Thus, the CLF gene appears to affect cell division at an earlier stage and cell elo ngation throughout the development of leaf primordia.