2015 Volume 32 Issue 1 Pages 65-79
A comprehensive analysis of the levels of primary metabolites in wild type (WT) and several auxin-signaling mutants namely, tir1, slr and arf7 arf19 of Arabidopsis thaliana has been performed using CE-MS, a technique particularly sensitive for the measurement of polar compounds. We first measured the levels of primary metabolites in shoots and roots, most of the analyzed metabolites were found to be quantitatively and qualitatively comparable in WT and three kinds of mutants (tir1, slr and arf7 arf19). Some amino acids such as GABA, Arg, Orn, Val, Thr, Leu and Ile exhibited a unique pattern of distribution between shoots and roots in both WT and the mutants. On the other hand, the mutant slr showed a quite different pattern of metabolites measured in the present study.
Subsequently, the responses of primary metabolites to a short-term (60 min) application of exogenous IAA (10−7, 10−8 M) in WT and the mutants were characterized. Due to IAA treatments, some amino acids such as GABA in WT roots and Gly and Ala in WT shoots were altered, but not in the mutants. Gln was altered in slr shoots by 10−7 M IAA treatment. Levels of G6P from the glycolic pathway were altered in WT roots and those of 2PG, 3PG were altered in tir1 shoots in response to IAA treatments. The levels of succinate in TCA cycle were altered by IAA treatments in WT shoots but not in the mutants. IAA treatment inhibited the respiration in WT roots. The suppression of respiration might account for the IAA-dependent alteration of some metabolites. Difference of auxin responses between WT and auxin-signaling mutants suggests that some metabolic processes are under IAA control.