Characterization of an Arabidopsis gene that mediates cytokinin signaling in shoot apical meristem development.
Cytokinins are adenine derivatives that regulate numerous plant growth and developmental processes, including apical and floral meristem development, stem growth, leaf senescence, apical dominance, and stress tolerance. However, not much is known about how cytokinin biosynthesis and metabolism is regulated. We identified a novel Arabidopsis gene, ALL, encoding an aldolase-like enzyme that regulates cytokinin signaling. An Arabidopsis mutant, all-1D, in which ALL is activated by the nearby insertion of the 35S enhancer, exhibited extreme dwarfism with rolled, dark-green leaves and reduced apical dominance, symptomatic of cytokinin-overproducing mutants. Consistent with this, ARR4 and ARR5, two representative primary cytokinin-responsive genes, were significantly induced in all-1D. Whereas SHOOT MERISTEMLESS (STM) and KNAT1, which regulate meristem development, were also greatly induced, expression of REV and PHV that regulate lateral organ polarity was inhibited. ALL encodes an aldolase-like enzyme that belongs to the HpcH/HpaI aldolase family in prokaryotes and is down-regulated by exogenous cytokinin, possibly through a negative feedback pathway. We propose that ALL is involved in cytokinin biosynthesis or metabolism and acts as a positive regulator of cytokinin signaling during shoot apical meristem development and determination of lateral organ polarity.
Jung
Jae-Hoon
JH
School of Chemistry, Seoul National University, Seoul 151-742, Korea.
Yun
Ju
J
Seo
Yeon-Hee
YH
Park
Chung-Mo
CM
D000446:Aldehyde-Lyases / Q000235:genetics*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000096:biosynthesis / Q000235:genetics*; D003583:Cytokinins / Q000502:physiology*; D017343:Genes, Plant / Q000502:physiology*; D018519:Meristem / Q000254:growth & development* / Q000502:physiology; D008969:Molecular Sequence Data; D015398:Signal Transduction / Q000187:drug effects; D015854:Up-Regulation
C113359:ARR4 protein, Arabidopsis; D029681:Arabidopsis Proteins; D003583:Cytokinins; C504901:ALL protein, Arabidopsis; D000446:Aldehyde-Lyases