© 2008 The Author(s).
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RESEARCH PAPER |
Transcription factors relevant to auxin signalling coordinate broad-spectrum metabolic shifts including sulphur metabolism
1Max-Planck-Institut fuer Molekulare Pflanzenphysiologie, Wissenschaftspark Golm, 14424 Potsdam, Germany
2Universität Potsdam, Institut fuer Biochemie und Biologie, Karl-Liebknecht-Str. 24–25, Haus 20, 14476 Potsdam-Golm, Germany
* To whom correspondence should be addressed. E-mail: hesse{at}mpimp-golm.mpg.de
A systems approach has previously been used to follow the response behaviour of Arabidopsis thaliana plants upon sulphur limitation. A response network was reconstructed from a time series of transcript and metabolite profiles, integrating complex metabolic and transcript data in order to investigate a potential causal relationship. The resulting scale-free network allowed potential transcriptional regulators of sulphur metabolism to be identified. Here, three sulphur-starvation responsive transcription factors, IAA13, IAA28, and ARF-2 (ARF1-Binding Protein), all of which are related to auxin signalling, were selected for further investigation. IAA28 overexpressing and knock-down lines showed no major morphological changes, whereas IAA13- and ARF1-BP-overexpressing plants grew more slowly than the wild type. Steady-state metabolite levels and expression of pathway-relevant genes were monitored under normal and sulphate-depleted conditions. For all lines, changes in transcript and metabolite levels were observed, yet none of these changes could exclusively be linked to sulphur stress. Instead, up- or down-regulation of the transcription factors caused metabolic changes which in turn affected sulphur metabolism. Auxin-relevant transcription factors are thus part of a complex response pattern to nutrient starvation that serve as coordinators of the metabolic shifts driving sulphur homeostasis rather then as direct effectors of the sulphate assimilation pathway. This study provides the first evidence ever presented that correlates auxin-related transcriptional regulators with primary plant metabolism.
Key words: Auxin, sulphur metabolism, systems biology, transcription factors
Received 14 March 2008; Revised 22 April 2008 Accepted 28 April 2008