title: The Arabidopsis AtIPT8/PGA22 gene encodes an isopentenyl transferase that is involved in de novo cytokinin biosynthesis.
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.
authors.affiliation: Institute of Genetics and Developmental Biology, Chinese Acadamy of Sciences, Beijing, China.
authors.forename: Jiaqiang
authors.initials: J
authors.lastname: Sun
authors.forename: Qi-Wen
authors.initials: QW
authors.lastname: Niu
authors.forename: Petr
authors.initials: P
authors.lastname: Tarkowski
authors.forename: Binglian
authors.initials: B
authors.lastname: Zheng
authors.forename: Danuse
authors.initials: D
authors.lastname: Tarkowska
authors.forename: Göran
authors.initials: G
authors.lastname: Sandberg
authors.forename: Nam-Hai
authors.initials: NH
authors.lastname: Chua
authors.forename: Jianru
authors.initials: J
authors.lastname: Zuo
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003583:Cytokinins / Q000096:biosynthesis*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D007541:Isopentenyladenosine / Q000378:metabolism; D013058:Mass Spectrometry; D009154:Mutation; D010641:Phenotype; D010937:Plant Growth Regulators / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018520:Plant Shoots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; D003583:Cytokinins; D010937:Plant Growth Regulators; D007541:Isopentenyladenosine; D019883:Alkyl and Aryl Transferases; C024274:adenylate isopentenyltransferase