Ethylene signaling cross-talk with other hormones in Arabidopsis thaliana exposed to contrasting phosphate availability: Differential effects in roots, leaves and fruits

Ethylene signaling plays a major role in the regulation of plant growth, but its cross-talk with other phytohormones is still poorly understood. Here, we investigated whether or not a defect in ethylene signaling, particularly in the ETHYLENE INSENSITIVE3 (EIN3) transcription factor, alters plant growth and influences the contents of other phytohormones. With this aim, a hormonal profiling approach using ultrahigh performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) was used to unravel organ-specific responses (in roots, leaves and fruits) in the ein3-1 mutant and wild-type A. thaliana plants exposed to contrasting phosphate (Pi) availability. A defect in ethylene signaling in the ein3-1 mutant increased the biomass of roots, leaves and fruits, both at 0.5 mM and 1 mM Pi, thus indicating the growth-inhibitory role of ethylene in all tested organs. The hormonal profiling in roots revealed a cross-talk between ethylene signaling and other phytohormones, as indicated by increases in the contents of auxin, gibberellins and the stress-related hormones, abscisic acid, salicylic acid and jasmonic acid. The ein3-1 mutant also showed increased cytokinin contents in leaves. Reduced Pi availability (from 1 mM to 0.5 mM Pi) affected fruit growth, but not root and leaf growth, thus indicating mild Pi deficiency. It is concluded that ethylene signaling plays a major role in the modulation of plant growth in A. thaliana and that the ein3-1 mutant is not only altered in ethylene signaling but in the contents of several phytohormones in an organ-specific manner, thus indicating a hormonal cross-talk.