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Open AccessHighly AccessResearch article

A system biology approach highlights a hormonal enhancer effect on regulation of genes in a nitrate responsive "biomodule"

Damion Nero* 1 email, Gabriel Krouk* 1 email, Daniel Tranchina1,2 email and Gloria M Coruzzi1 email

1Center for Genomics and Systems Biology, Department of Biology, New York University, 100 Washington Square East, 1009 Main Building, New York, 10003, USA

2Courant Institute of Mathematical Sciences, New York, 251 Mercer St, New York, NY, 10012, USA

author email corresponding author email* Contributed equally

BMC Systems Biology 2009, 3:59doi:10.1186/1752-0509-3-59

Published: 6 June 2009

Abstract

Background

Nitrate-induced reprogramming of the transcriptome has recently been shown to be highly context dependent. Herein, a systems biology approach was developed to identify the components and role of cross-talk between nitrate and hormone signals, likely to be involved in the conditional response of NO3- signaling.

Results

Biclustering was used to identify a set of genes that are N-responsive across a range of Nitrogen (N)-treatment backgrounds (i.e. nitrogen treatments under different growth conditions) using a meta-dataset of 76 Affymetrix ATH1 chips from 5 different laboratories. Twenty-one biclusters were found to be N-responsive across subsets of this meta-dataset. N-bicluster 9 (126 genes) was selected for further analysis, as it was shown to be reproducibly responsive to NO3- as a signal, across a wide-variety of background conditions and datasets. N-bicluster 9 genes were then used as "seed" to identify putative cross-talk mechanisms between nitrate and hormone signaling. For this, the 126 nitrate-regulated genes in N-bicluster 9 were biclustered over a meta-dataset of 278 ATH1 chips spanning a variety of hormone treatments. This analysis divided the bicluster 9 genes into two classes: i) genes controlled by NO3- only vs. ii) genes controlled by both NO3- and hormones. The genes in the latter group showed a NO3- response that is significantly enhanced, compared to the former. In silico analysis identified two Cis-Regulatory Elements candidates (CRE) (E2F, HSE) potentially involved the interplay between NO3- and hormonal signals.

Conclusion

This systems analysis enabled us to derive a hypothesis in which hormone signals are proposed to enhance the nitrate response, providing a potential mechanistic explanation for the link between nitrate signaling and the control of plant development.


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