Genome-wide expression profiling of ARABIDOPSIS RESPONSE REGULATOR 7(ARR7) overexpression in cytokinin response
- 1.9k Downloads
The type-A ARRs of cytokinin two-component signaling system act as negative regulators for cytokinin signaling except for ARR4, but the molecular mechanism by which the A-type ARRs regulate cytokinin signaling remain elusive. To get insights into the molecular function of A-type ARR in cytokinin response, we sought to find the components that function downstream of A-type ARR protein by investigating the effects of ARR7 overexpression on cytokinin-regulated gene expression with the Affymetrix full genome array. To examine early cytokinin response, plants were treated with cytokinin for 30 min or 2 h, followed by GeneChip analysis. The hierarchical clustering analysis of our GeneChip data showed that ARR7 overexpression had distinctively repressive impacts on various groups of the cytokinin-regulated genes. In particular, the induction of all A-type ARRs except for ARR22, and AHK(ARABIDOPSIS HISTIDINE KINASE)1 and AHK4 was suppressed by ARR7. Cytokinin-induced expression of most of 12 expansin genes were repressed by ARR7, indicating potential involvement of ARR7 in cell expansion and plant development. Up-regulation of five cytokinin oxidase genes by cytokinins was negatively affected by ARR7. Our GeneChip analysis suggest that ARR7 mainly acts as a transcriptional repressor for a variety of early cytokinin-regulated genes encoding transcription factors, signal transmitters, plant development, and cellular metabolism, which may be responsible for reduced sensitivity of Arabidopsis transgenic plants overexpressing ARR7 to exogenous cytokinins.
KeywordsArabidopsis response regulator Cytokinin signal transduction Expansin GeneChip Plant hormone
This work was supported by grants from the Plant Diversity Research Center of 21st Century Frontier Research Program (PF0330404-02), funded by the Ministry of Science and Technology of Korean government and from the Agricultural Plant Stress Research Center (R11-20010003101-0) funded by Korea Science and Engineering Foundation to J. Kim. We thank Seoulin Bioscience for technical assistance with GeneChip analysis.
- Brenner WG, Romanov GA, Köllmer I, Bürkle L, Schmülling T (2005) Immediate-early and delayed cytokinin response genes of Arabidopsis thaliana identified by genome-wide expression profiling reveal novel cytokinin-sensitive processes and suggest cytokinin action through transcriptional cascades. Plant J 44:314–333PubMedCrossRefGoogle Scholar
- Davies PJ (ed) (2004) Plant hormones biosynthesis, signal transduction, action. Kluwer Academic Publishers, The NetherlandsGoogle Scholar
- Inukai Y, Sakamoto T, Ueguchi-Tanaka M, Shibata Y, Gomi K, Umemura I, Hasegawa Y, Ashikari M, Kitano H, Matsuoka M (2005) Crown rootless1, which is essential for crown root formation in rice, is a target of an AUXIN RESPONSE FACTOR in auxin signaling. Plant Cell 17:1387–1396PubMedCrossRefGoogle Scholar
- Iwakawa H, Ueno Y, Semiarti E, Onouchi H, Kojima S, Hirokazu T, Hasebe M, Soma T, Ikezaki M, Machida C, Machida Y (2002) The ASYMMETRIC LEAVES2 gene of Arabidopsis thaliana, required for formation of a symmetric flat leaf lamina, encodes a member of a novel family of proteins characterized by cysteine repeats and a leucine zipper. Plant Cell Physiol 43:467–478PubMedCrossRefGoogle Scholar
- Leibfried A, To JPC, Busch W, Stehling S, Kehle A, Demar M, Kieber JJ, Lohmann JU (2005) WUSCHEL controls meristem function by direct regulation of cytokinin-inducible response regulators. Nature 438:22–29Google Scholar
- Okushima Y, Overvoorde PJ, Arima K, Alonso JM, Chan A, Chang C, Ecker JR, Hughes B, Lui A, Nguyen D, Onodera C, Quach H, Smith A, Yu G, Theologis A (2005) Functional genomic analysis of the AUXIN RESPONSE FACTOR gene family members in Arabidopsis thaliana: unique and overlapping functions of ARF7 and ARF19. Plant Cell 17:444–463PubMedCrossRefGoogle Scholar
- Osakabe Y, Miyata S, Urao T, Seki M, Shinozaki K, Yamaguchi-Shinozaki K (2002) Overexpression of Arabidopsis response regulators, ARR4/ATRR1/IBC7 and ARR8/ATRR3, alters cytokinin responses differentially in the shoot and in callus formation. Biochem Biophys Res Commun 293:806–815PubMedCrossRefGoogle Scholar
- Vernon LP (1960) Spectrophotometric determination of chlorophyll and pheophytins in plant extracts. Anal Chem 32:1142–1150Google Scholar