Poster: Late and Moved Abstracts

Abs # 1425: Auxin promotes Arabidopsis root growth by modulating gibberellin response

Presenter:	Fu, Xiangdong , xiangdong.fu@bbsrc.ac.uk
Authors	Fu, Xiangdong  (A)   Fu, Xiangdong  (A)   Nicholas, Harberd P (A)
Affiliations:	(A): John Innes Centre

The growth of plant organs is influenced by a stream of the phytohormone auxin that flows from the shoot apex to the tip of the root1. However, until now, it was not known how auxin regulates the cell proliferation and enlargement that characterizes organ growth. Here we show that auxin controls the growth of roots by modulating cellular responses to the phytohormone gibberellin. GA promotes the growth of plants by opposing the effects of nuclear DELLA protein growth repressors, one of which is Arabidopsis RGA. GA opposes the action of several DELLA proteins by destabilising them, reducing both the level of detectable DELLA proteins and their growth-restraining effects. In this paper we show that shoot apex-derived auxin is necessary for GA-mediated control of root growth. Furthermore, we show that attenuation of auxin transport or signalling delays the GA-induced disappearance of RGA from root cell nuclei. Our observations indicate that the shoot apex exerts long-distance control on the growth of plant organs via the effect of auxin on GA-mediated DELLA protein destabilisation.