Characterization of the response of the Arabidopsis response regulator gene family to cytokinin.

We examined the expression of a family of Arabidopsis response regulators (ARR) and found that the steady-state levels of RNA for most are elevated very rapidly by cytokinin. Using nuclear run-on assays we demonstrated that this increase in ARR transcript levels in response to cytokinin is due, at least in part, to increased transcription. The start site of transcription for the ARR5 gene was identified using primer extension analysis. A DNA fragment comprised of 1.6 kb upstream of the ARR5 transcript start site conferred cytokinin-inducible gene expression when fused to a beta-glucuronidase reporter, confirming that the transcription rate of ARR5 is elevated by cytokinin. This reporter construct was also used to examine the spatial pattern of ARR5 expression. The highest levels of expression were observed in the root and shoot apical meristems, at the junction of the pedicle and the silique, and in the central portion of mature roots. The expression of ARR5 in the apical meristems was confirmed by whole mount in situ analysis of seedlings and is consistent with a role for cytokinin in regulating cell division in vivo.

[1]  R. W. Davis,et al.  Rapid induction of specific mRNAs by auxin in pea epicotyl tissue. , 1985, Journal of molecular biology.

[2]  A A Szalay,et al.  Dual promoter of Agrobacterium tumefaciens mannopine synthase genes is regulated by plant growth hormones. , 1989, Proceedings of the National Academy of Sciences of the United States of America.

[3]  T. Schmülling,et al.  Cytokinins as regulators of gene expression , 1997 .

[4]  A. Theologis,et al.  Transcriptional Regulation ofPS-IAA4/5andPS-IAA6Early Gene Expression by Indoleacetic Acid and Protein Synthesis Inhibitors in Pea(Pisum sativum) , 1995 .

[5]  A. Theologis,et al.  The PS-IAA4/5-like family of early auxin-inducible mRNAs in Arabidopsis thaliana. , 1995, Journal of molecular biology.

[6]  V. Weiss,et al.  Signalling pathways in two-component phosphorelay systems. , 1999, Trends in microbiology.

[7]  G. Shaulsky,et al.  Histidine kinases in signal transduction pathways of eukaryotes. , 1997, Journal of cell science.

[8]  J. Medford,et al.  Alterations of Endogenous Cytokinins in Transgenic Plants Using a Chimeric Isopentenyl Transferase Gene. , 1989, The Plant cell.

[9]  J. Hoch,et al.  Two-component signal transduction , 1995 .

[10]  D. Mok.  Cytokinins: Chemistry, Activity, and Function , 1994 .

[11]  S. Clough,et al.  Floral dip: a simplified method for Agrobacterium-mediated transformation of Arabidopsis thaliana. , 1998, The Plant journal : for cell and molecular biology.

[12]  H. Herschman.  Primary response genes induced by growth factors and tumor promoters. , 1991, Annual review of biochemistry.

[13]  C. Chen,et al.  Transcriptional regulation of nitrate reductase mRNA levels by cytokinin-abscisic Acid interactions in etiolated barley leaves. , 1992, Plant physiology.

[14]  J. Van De Sande,et al.  5'-32P labeling of RNA and DNA restriction fragments. , 1980, Methods in enzymology.

[15]  T. Mizuno,et al.  Compilation and characterization of Arabidopsis thaliana response regulators implicated in His-Asp phosphorelay signal transduction. , 1999, Plant & cell physiology.

[16]  F. Skoog,et al.  KINETIN, A CELL DIVISION FACTOR FROM DEOXYRIBONUCLEIC ACID1 , 1955 .

[17]  J. S. Parkinson.  Signal transduction schemes of bacteria , 1993, Cell.

[18]  M. Bevan,et al.  GUS fusions: beta‐glucuronidase as a sensitive and versatile gene fusion marker in higher plants. , 1987, The EMBO journal.

[19]  F. D. de Bruijn,et al.  Posttranscriptional Regulation of the Sesbania rostrata Early Nodulin Gene SrEnod2 by Cytokinin , 1996, Plant physiology.

[20]  E. Meyerowitz,et al.  Arabidopsis ethylene-response gene ETR1: similarity of product to two-component regulators. , 1993, Science.

[21]  F. Sanger,et al.  DNA sequencing with chain-terminating inhibitors. , 1977, Proceedings of the National Academy of Sciences of the United States of America.

[22]  H. Sakakibara,et al.  A response-regulator homologue possibly involved in nitrogen signal transduction mediated by cytokinin in maize. , 1998, The Plant journal : for cell and molecular biology.

[23]  F. Skoog,et al.  Isolation, Structure and Synthesis of Kinetin, a Substance Promoting Cell Division1,2 , 1956 .

[24]  K. Folta,et al.  Preparation of transcriptionally active nuclei from etiolated Arabidopsis thaliana , 2000, Plant Cell Reports.

[25]  T. Mizuno,et al.  Genes encoding pseudo-response regulators: insight into His-to-Asp phosphorelay and circadian rhythm in Arabidopsis thaliana. , 2000, Plant & cell physiology.

[26]  T. Mizuno,et al.  Expression of Arabidopsis response regulator homologs is induced by cytokinins and nitrate , 1998, FEBS letters.

[27]  Azmi,et al.  Dynamics of cytokinins in apical shoot meristems of a day-neutral tobacco during floral transition and flower formation , 1999, Plant physiology.

[28]  F. B. Pickett,et al.  Seeing double: appreciating genetic redundancy. , 1995, The Plant cell.

[29]  J. Kieber,et al.  Phosphorelay signal transduction: the emerging family of plant response regulators. , 1999, Trends in biochemical sciences.

[30]  T. Mizuno,et al.  Differential expression of genes for response regulators in response to cytokinins and nitrate in Arabidopsis thaliana. , 1999, Plant & cell physiology.

[31]  S. Howell,et al.  Cytokinins and auxins control the expression of a gene in Nicotiana plumbaginifolia cells by feedback regulation. , 1992, The Plant cell.

[32]  K. Shinozaki,et al.  Stress‐responsive expression of genes for two‐component response regulator‐like proteins in Arabidopsis thaliana , 1998, FEBS letters.

[33]  T. Guilfoyle,et al.  Induction and superinduction of auxin-responsive mRNAs with auxin and protein synthesis inhibitors. , 1990, The Journal of biological chemistry.

[34]  R. Angerer,et al.  Detection of mrnas in sea urchin embryos by in situ hybridization using asymmetric RNA probes. , 1984, Developmental biology.

[35]  Joseph J. Kieber,et al.  Two Genes with Similarity to Bacterial Response Regulators Are Rapidly and Specifically Induced by Cytokinin in Arabidopsis , 1998, Plant Cell.

[36]  R C Stewart,et al.  The two-component system. Regulation of diverse signaling pathways in prokaryotes and eukaryotes. , 1998, Plant physiology.

[37]  J. Stock,et al.  Signal transduction in bacteria , 1990, Nature.

[38]  T. Kakimoto.  CKI1, a Histidine Kinase Homolog Implicated in Cytokinin Signal Transduction , 1996, Science.

[39]  A. Theologis,et al.  ThePS-IAA4/5-like Family of Early Auxin-inducible mRNAs inArabidopsis thaliana , 1995 .

[40]  B. Scheres,et al.  Cellular organisation of the Arabidopsis thaliana root. , 1993, Development.