Ethylene–auxin interactions regulate lateral root initiation and emergence in Arabidopsis thaliana
Article first published online: 24 APR 2008
© 2008 The Authors. Journal compilation © 2008 Blackwell Publishing Ltd
The Plant Journal
Volume 55, Issue 2, pages 335–347, July 2008
How to Cite
Ivanchenko, M. G., Muday, G. K. and Dubrovsky, J. G. (2008), Ethylene–auxin interactions regulate lateral root initiation and emergence in Arabidopsis thaliana. The Plant Journal, 55: 335–347. doi: 10.1111/j.1365-313X.2008.03528.x
- Issue published online: 8 JUL 2008
- Article first published online: 24 APR 2008
- Received 26 February 2008; revised 4 April 2008; accepted 8 April 2008.
- lateral root primordia;
- root development;
Plant root systems display considerable plasticity in response to endogenous and environmental signals. Auxin stimulates pericycle cells within elongating primary roots to enter de novo organogenesis, leading to the establishment of new lateral root meristems. Crosstalk between auxin and ethylene in root elongation has been demonstrated, but interactions between these hormones in root branching are not well characterized. We find that enhanced ethylene synthesis, resulting from the application of low concentrations of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), promotes the initiation of lateral root primordia. Treatment with higher doses of ACC strongly inhibits the ability of pericycle cells to initiate new lateral root primordia, but promotes the emergence of existing lateral root primordia: behaviour that is also seen in the eto1 mutation. These effects are correlated with decreased pericycle cell length and increased lateral root primordia cell width. When auxin is applied simultaneously with ACC, ACC is unable to prevent the auxin stimulation of lateral root formation in the root tissues formed prior to ACC exposure. However, in root tissues formed after transfer to ACC, in which elongation is reduced, auxin does not rescue the ethylene inhibition of primordia initiation, but instead increases it by several fold. Mutations that block auxin responses, slr1 and arf7 arf19, render initiation of lateral root primordia insensitive to the promoting effect of low ethylene levels, and mutations that inhibit ethylene-stimulated auxin biosynthesis, wei2 and wei7, reduce the inhibitory effect of higher ethylene levels, consistent with ethylene regulating root branching through interactions with auxin.