title: Differences and similarities in the photoregulation of gibberellin metabolism between rice and dicots.
abstract: In rice seedlings, elongation of leaf sheaths is suppressed by light stimuli. The response is mediated by two classes of photoreceptors, phytochromes and cryptochromes. However, it remains unclear how these photoreceptors interact in the process. Our recent study using phytochrome mutants and novel cryptochrome RNAi lines revealed that cryptochromes and phytochromes function cooperatively, but independently to reduce active GA contents in seedlings in visible light. Blue light captured by cryptochrome 1 (cry1a and cry1b) induces robust expression of GA 2-oxidase genes (OsGA2ox4-7). In parallel, phytochrome B with auxiliary action of phytochrome A mediates repression of GA 20-oxidase genes (OsGA20ox2 and OsGA20ox4). The independent effects cumulatively reduce active GA contents, leading to a suppression of leaf sheath elongation. These regulatory mechanisms are distinct from phytochrome B function in dicots. We discuss reasons why the distinct system appeared in rice, and advantages of the rice system in early photomorphogenesis.
authors: Functional Plant Research Unit; National Institute of Agrobiological Sciences; Tsukuba, Ibaraki Japan.
authors: Fumiaki
authors: F
authors: Hirose
authors: Noritoshi
authors: N
authors: Inagaki
authors: Makoto
authors: M
authors: Takano
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D056931:Cryptochromes / Q000378:metabolism; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005875:Gibberellins / Q000235:genetics* / Q000378:metabolism; D008027:Light; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism; D012275:Oryza / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D051942:Phytochrome A / Q000378:metabolism; D051939:Phytochrome B / Q000378:metabolism; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D036226:Seedlings / Q000254:growth & development / Q000378:metabolism
chemical_list: D056931:Cryptochromes; D005875:Gibberellins; D051942:Phytochrome A; D010940:Plant Proteins; D051939:Phytochrome B; D006899:Mixed Function Oxygenases; C089210:gibberellin, 2-oxoglutarate-oxygen oxidoreductase (20-hydroxylating, oxidizing)
keywords: cryptochrome; gibberellin (GA); leaf sheath elongation; photomorphogenesis; phytochrome; rice (Oryza sativa)