Isolation and characterization of an Arabidopsis mutant, fireworks (fiw), which exhibits premature cessation of inflorescence growth and early leaf senescence

To examine the mechanism underlying the reproductive development in monocar pic plants, we screened for mutants that exhibit premature cessation of inf lorescence growth in Arabidopsis. We identified a novel mutant line that ex hibited earlier cessation of flower formation and inflorescence stem elonga tion. This mutant also exhibited accelerated rosette leaf senescence after the cessation of the inflorescence growth. We designated the mutant firewor ks (fiw) because flowers and siliques were clustered at the top of the fiw inflorescence. The fiw mutation was a single, recessive mutation and mapped on the lower part of chromosome 4. The fiw phenotype was not observable du ring vegetative growth, but the inflorescence growth was arrested more than 7d earlier than the wild type (WT). Microscopic observation revealed that the fiw apical meristem was structurally preserved. The premature arrest of growth was observed not only in the primary inflorescence but also in the lateral inflorescence, which is consistent with the global proliferative ar rest observed later in WT. Regardless of such dramatic phenotypic features, the fiw plants bore normal powers and set fully matured siliques.