Os02g0325600

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Annotated Information

Function

the gene encoding a putative GARP-type transcription factor (Os02g0325600) from rice (Oryza sativa L.), which was designated NIGT1 (NitrateI nducible,GARP-type Transcriptional Repressor 1). NIGT1 is a nitrate-inducible and autorepressible transcriptional repressor which might be involved in control of nitrate utilization. The transcriptome analysis of nitrogen response pathways in rice has indicated that several genes encoding putative transcription factors are induced by the supply of ammonium nitrate and also that NIGT1 was one of the earliest and most strongly induced genes. It encodes a novel transcriptional repressor of the regulatory network underlying the nitrate response in rice. More significantly, the identification of such a transcription factor suggests the presence of a complex mechanism of transcriptional regulation for an appropriate nitrogen response in plants. NIGT1 is a member of a subgroup for which the DNA binding activity has not been previously reported for any member. the DNA binding activity of NIGT1 in a DNA-binding site selection experiment using a library of randomly synthesized DNA and recombinant NIGT1 Protein.

NIGT1 is a transcriptional repressor The activity of NIGT1 as a transcription factor was examined by co-transfection of various reporter and effector constructs into maize mesophyll protoplasts and measurement of reporter enzyme activity. The expression of NIGT1 could not activate transcription from the promoter containing four copies of the core-1 sequence or two copies of the core-2 sequence upstream of the 35S minimal promoter, whereas NIGT1 fused to the transcriptional activation Domain of VP16 (NIGT1¨CVP16) was found to promote transcription from these promoters. The activity of NIGT1 is a transcription factor. Similar to LexA¨CSUPRD, the expression of LexA¨CNIGT1 fusion protein down-regulated reporter enzyme activity, indicating that NIGT1 is a transcriptional repressor.

Expression

Nitrate induces the expression of the NIGT1 gene in rice NIGT1 expression was found to be induced by nitrate but not ammonium, glutamine or trans-zeatin, a plant hormone involved in the nitrate response. Nitrate is a signaling molecule even in rice, and that it transiently induces the expression of a nuclear protein, NIGT1.

NIGT1 represses its own promoter activity NIGT1 autoregulates its expression negatively through conserved consensus sites in its own promoter.

Reduced expression of endogenous NIGT1 in transgenic rice plants overexpressing NIGT1 the expression of the introduced NIGT1 was much stronger than that of the endogenous gene. As expected from the strong expression of the introduced NIGT1 gene, qRT¨CPCR analysis revealed that the nitrate-induced expression level of endogenous NIGT1 was lower in the NIGT1 overexpressors, although the effects of this overexpression was limited under conditions of nitrate absence.

Effects of overexpressed NIGT1 on the chlorophyll content the expression levels of these genes in the NIGT1 overexpressors but did not find any significant modulations in their expression levels.

Evolution

none

=Labs working on this gene

Biotechnology Research Center, The University of Tokyo;

Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo;

Division of Plant Sciences, National Institute of Agrobiological Sciences, Kannondai, Tsukuba, Ibaraki.

References

1 Naoya Sawaki;Ryoma Tsujimoto;Mikao Shigyo;Mineko Konishi;Seiichi Toki;Toru Fujiwara;Shuichi Yanagisawa. A Nitrate-Inducible GARP Family Gene Encodes an Auto-Repressible Transcriptional Repressor in Rice. Plant and Cell Physiology, 2013, 54(4): 506-517.

2 Konishi, M. and Yanagisawa, S. (2008) Ethylene signaling in Arabidopsis involves feedback regulation via the elaborate control of EBF2 expression by EIN3. Plant J. 55: 821¨C831.

3 Husbands, A., Bell, E.M., Shuai, B., Smith, H.M. and Springer, P.S. (2007) LATERAL ORGAN BOUNDARIES defines a new family of DNA-binding transcription factors and can interact with specific bHLH proteins. Nucleic Acids Res. 35: 6663¨C6671.

4 Aki, T. and Yanagisawa, S. (2009) Application of rice nuclear proteome analysis to the identification of evolutionarily conserved and glucose-responsive nuclear proteins. J. Proteome Res. 8: 3912¨C3924