Amongst their numerous roles in plants, flavonoid pigments are hypothesised to affect growth and development via interactions with components of auxin transport networks. Accordingly, our previous work showed that a multidrug and toxin efflux family transporter (FFT) alters root and seed characteristics and was required for full fertility in Arabidopsis. FFT is transcribed in guard cells throughout the plant and inactivation of FFT caused a significant perturbation in flavonoid profile in floral organs. Indeed, SEM and viability staining of mutant flowers reveal reduced anther dehiscence and a proportion of defective pollen, while siliques are smaller with fewer seeds than in WT. Null mutant seedlings grow faster and bolt sooner than WT, and seed size and mucilage are also affected. We are currently quantifying in more detail the flavonoid content of fft plants, and investigating the effect of externally applied auxin, flavonols and an auxin transport inhibitor. Finally, since we see FFT- promoter-GUS induced staining in vegetative tissues, including hydathode guard cells, we are also examining the abiotic stress response in the fft mutant. Co-expressed genes are involved in drought response including salt and osmotic stress
