Abstract
Axillary buds developing at the axils of leaves produce additional shoot systems, lateral branches. The rice TB1 gene (OsTB1) was first identified based on its sequence similarity with maize TEOSINTE BRANCHED 1 (TB1), which is involved in lateral branching in maize. Both genes encode putative transcription factors carrying a basic helix-loop-helix type of DNA-binding motif, named the TCP domain. Transgenic rice plants overexpressing OsTB1 exhibited markedly reduced lateral branching without the propagation of axillary buds. We also demonstrated that a rice strain carrying a classical marker mutation, fine culm 1 (fc1), contains the loss-of-function mutation of OsTB1 and exhibits enhanced lateral branching. Expression of OsTB1 was observed throughout the axillary bud, as well as the basal part of the shoot apical meristem, vascular tissues in the pith and the lamina joint. Taking these data together, we concluded that OsTB1 functions as a negative regulator for lateral branching in rice.
