Abstract
Apical dominance prioritizes primary inflorescence, repressing the growth of lateral branches. In our study, we found an Arabidopsis mutant that appeared to have lost apical dominance. The mutant plant elongated its lateral branches for prolonged duration without growth repression, and its final architecture was like a bird's nest. We termed the mutation responsible for the phenotype as noah (no apical dominance in branch hierarchy), and studied the mechanism underlying the formation of the monstrous architecture. Detailed study revealed that the mutant stems were somehow immune to growth repression by apical dominance, and that the prolonged elongation of the mutant stems allowed repeated cycles of branching and stem elongation in the mutant plants. Since auxin is believed to induce stem elongation, we next analyzed auxin distribution along the mutant stems. The result demonstrated that noah stems exhibit auxin distribution strikingly different from that in WT stems. It was therefore suggested that the noah mutation had affected significantly the polar auxin transport in the mutant stems.
