DELLA dependent interaction between Gibberellic acid signal transduction and Auxin transport

The phytohormone auxin (IAA) plays a major role in the regulation of multiple aspects of plant development and growth. Auxin and gibberellic acid (GA) functionally overlap in their effects on shoot and root growth. We propose that these two hormones interact to regulate common targets. We investigate possible IAA-GA cross-talk by studying the effect of gibberellic acid on auxin-related plant development and physiology like lateral root development and the gravitropic response of shoots and roots. During lateral root development and gravitropism auxin gradients are established by polar auxin transport. Directional auxin transport is achieved by polar localisation of auxin-efflux carriers encoded by PIN genes. We study the impact of GA on polar auxin transport and investigate GA effects on PIN protein amount and localisation. GA signal transduction involves degradation of DELLA repressor proteins. We use mutants defective in expression or function of the DELLA repressors to obtain hints on the cross-talk between GA signal transduction and auxin signalling and transport.

1. Visualisation of the auxin efflux carrier PIN2 as GFP fusion protein in the Arabidopsis root

2. Nuclear localization of the DELLA protein RGA fused to GFP