Symposium III: Hormone Crosstalk

Abs # 30004: The hormonal control of shoot branching in Arabidopsis

Presenter:	Leyser, Ottoline , hmol1@york.ac.uk
Authors	Leyser, Ottoline  ( )
Affiliations:	(A): University of York

Auxin has a major role in regulating shoot branching. Classical studies have demonstrated that apically-derived auxin, moving down the plant in the polar transport stream, can inhibit lateral branching by suppressing axillary bud growth. However, work with radio-labelled auxin has demonstrated that auxin mediates this inhibition without entering the bud. We are studying the mechanism of action of auxin in the inhibition of bud development. We have used Arabidopsis auxin resistant mutants to define the role of auxin in bud growth in vivo and to establish the site of auxin action. In addition we have isolated mutants at 4 new loci, called MAX1-MAX4, with increased shoot branching and we are characterising the role of these loci in the control of bud growth. The genes appear to define a pathway that is required for wild-type auxin-mediated bud inhibition. Grafting studies have demonstrated that three of these loci are involved in the production of a long-range graft transmissible signal that may act downstream of auxin to inhibit bud growth.