Table I. Combination mutants used in this study were made by crossing previously characterized single and double mutants.

Mutants	Mutation(s)	Description
ibr1a	Arg → Cys	Short-chain dehydrogenase; disruption leads to IBA response phenotypes in root elongation, lateral root initiation
ibr3b	Glu → Lys, splice site mutation	Acyl-CoA dehydrogenase; disruption leads to IBA response phenotypes in root elongation, lateral root initiation
mes17c	Transfer DNA (T-DNA) insertion	Methyl esterase; disruption leads to increased hypocotyl length and resistance to MeIAA
ill2 iar3d	T-DNA in ILL2	IAA-conjugate hydrolases; disruption leads to resistance to IAA-Ala
	T-DNA in IAR3
ill2 ilr1d	T-DNA in ILL2	IAA-conjugate hydrolases; disruption leads to resistance to IAA-Leu and IAA-Phe
	Deletion in ILR1
ill2 iar3 ibr3		Triple mutant combining disruptions in IBA response and IAA-conjugate hydrolysis
ill2 ilr1 iar3 ibr1		Quadruple mutant combining disruptions in IBA response and IAA-conjugate hydrolysis
mes17 ill2 iar3		Triple mutant combining disruptions in MeIAA hydrolysis and IAA-conjugate hydrolysis
mes17 ibr3		Double mutant combining disruptions in MeIAA hydrolysis and IBA response

^aZolman et al. (2008). ^bZolman et al. (2007). ^cYang et al. (2008). ^dRampey et al. (2004).