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PMID:12529525
| Citation |
Sun, J, Niu, QW, Tarkowski, P, Zheng, B, Tarkowska, D, Sandberg, G, Chua, NH and Zuo, J (2003) The Arabidopsis AtIPT8/PGA22 gene encodes an isopentenyl transferase that is involved in de novo cytokinin biosynthesis. Plant Physiol. 131:167-76 |
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| Abstract |
Cytokinin plays a critical role in plant growth and development by stimulating cell division and cell differentiation. Despite many years' research efforts, our current understanding of this hormone is still limited regarding both its biosynthesis and signaling. To genetically dissect the cytokinin pathway, we have used a functional screen to identify Arabidopsis gain-of-function mutations that enable shoot formation in the absence of exogenous cytokinins. By using a chemical-inducible activation tagging system, we have identified over 40 putative mutants, designated as pga (plant growth activators), which presumably were affected in key components of cytokinin biosynthesis and signaling pathway. Here, we report a detailed characterization of pga22, a representative mutant from this collection. A gain-of-function mutation in the PGA22 locus resulted in typical cytokinin responses. Molecular and genetic analyses indicated that PGA22 encodes an isopentenyl transferase (IPT) previously identified as AtIPT8. Plants of the pga22 mutant accumulated at remarkably higher levels of isopentenyladenosine-5'-monophosphate and isopentenyladenosine when analyzed by mass spectrometry, suggesting that AtIPT8/PGA22 is a functional IPT that may direct the biosynthesis of cytokinins in planta via an isopentenyladenosine-5'-monophosphate-dependent pathway. |
| Links |
PubMed PMC166797 Online version:10.1104/pp.011494 |
| Keywords |
Alkyl and Aryl Transferases/genetics; Alkyl and Aryl Transferases/metabolism; Arabidopsis/enzymology; Arabidopsis/genetics; Arabidopsis/growth & development; Arabidopsis Proteins/genetics; Arabidopsis Proteins/metabolism; Cytokinins/biosynthesis; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Isopentenyladenosine/metabolism; Mass Spectrometry; Mutation; Phenotype; Plant Growth Regulators/metabolism; Plant Roots/genetics; Plant Roots/growth & development; Plant Roots/metabolism; Plant Shoots/genetics; Plant Shoots/growth & development; Plant Shoots/metabolism; Signal Transduction/physiology |
| edit table |
Significance
Annotations
| Gene product | Qualifier | GO Term | Evidence Code | with/from | Aspect | Extension | Notes | Status |
|---|---|---|---|---|---|---|---|---|
| GO:0009824: AMP dimethylallyltransferase activity |
ECO:0000315: |
F |
Fig. 6 shows the activation of cytokinin marker genes in the pga22 gain-of-function mutant. Fig. 7 depicts increasing cytokinin levels in the pga22 mutant plants and AtIPT8 catalyzes the production isopentenyladenosine-5′-monophosphate (iPMP) and isopentenyladenosine (iPA). This suggests that AtIPT8/PGA22 may direct cytokinin biosynthesis.
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