Expression profiling of cytokinin action in Arabidopsis.
The phytohormone cytokinin is an important regulator of plant growth and development; however, relatively few genes that mediate cytokinin responses have been identified. Genome-wide analyses of Arabidopsis seedlings using the approximately 8,300-element Affymetrix Arabidopsis GeneChips (Affymetrix, Santa Clara, CA) to examine cytokinin-responsive genes were conducted, revealing at least 30 genes whose steady-state level of mRNA was elevated and at least 40 that were down-regulated at multiple time points after application of cytokinin. The cytokinin up-regulated genes include the type-A Arabidopsis response regulators (ARRs), which had been shown previously to be cytokinin primary response genes, cytokinin oxidase, which encodes an enzyme that degrades cytokinins, and several transcription factors. Cytokinin down-regulated genes include several peroxidases and kinases and an E3 ubiquitin ligase. We identified a common sequence motif enriched in the upstream regions of the most consistently cytokinin up-regulated genes. This motif is highly similar to the optimal DNA-binding sites for ARR1/ARR2, type-B ARRs that have been implicated in the transcriptional elevation of the type-A ARRs. Additionally, genome-wide analyses of cytokinin receptor mutants (wol/cre1) revealed large-scale changes in gene expression, including down-regulation of the type-A ARRs and several meristem and cell cycle genes, such as CycD3. Mutations in CRE1 reduced but did not eliminate the effect of cytokinin on gene expression for a subset of cytokinin-responsive genes and had little or no effect on others, suggesting functional redundancy among the cytokinin receptors.
Rashotte
Aaron M
AM
University of North Carolina, Biology Department, CB Number 3280, Chapel Hill, North Carolina 27599-3280, USA.
Carson
Susan D B
SD
To
Jennifer P C
JP
Kieber
Joseph J
JJ
D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000096:biosynthesis / Q000235:genetics; D003583:Cytokinins / Q000494:pharmacology*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D017343:Genes, Plant / Q000235:genetics; D009154:Mutation / Q000235:genetics; D011494:Protein Kinases / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics
D029681:Arabidopsis Proteins; D003583:Cytokinins; D011956:Receptors, Cell Surface; D011494:Protein Kinases; C421783:WOL protein, Arabidopsis