title: Nitrogen fertilizer increases spikelet number per panicle by enhancing cytokinin synthesis in rice.
abstract: Flower number per panicle is one of the most important traits in rice productivity determination. The number of flowers is established in the early stages of panicle development. Nitrogen fertilizer application before panicle initiation is well known to increase flower number. Nitrogen increases cytokinin (CKs) biosynthesis in plants, and CKs have very similar effects as nitrogen fertilizer on panicle branching. The effects of nitrogen fertilizer on panicle branching may be mediated by CKs, in which accumulation in the inflorescence meristem can regulate panicle development, resulting in increased numbers of flowers and branches. Adenosine phosphate-isopentenyltransferase (IPT) catalyzes the rate-limiting step of CKs biosynthesis. We analyzed the effect of nitrogen fertilizer (urea) on the expression of OsIPT genes (OsIPTs). The results showed that OsIPTs were markedly increased, and CKs accumulated in panicle when nitrogen fertilizer was applied. CKs biosynthesis in the roots and leaves was not up-regulated by nitrogen. These results suggest that nitrogen fertilizer enhances local CKs synthesis to increase flower numbers in the panicles of rice. Localized CKs biosynthesis is an important response to nitrogen.
authors.affiliation: College of Agriculture, Nanjing Agricultural University, Nanjing, 210095, Jiangsu, People's Republic of China.
authors.forename: Chengqiang
authors.initials: C
authors.lastname: Ding
authors.forename: Juan
authors.initials: J
authors.lastname: You
authors.forename: Lin
authors.initials: L
authors.lastname: Chen
authors.forename: Shaohua
authors.initials: S
authors.lastname: Wang
authors.forename: Yanfeng
authors.initials: Y
authors.lastname: Ding
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics; D003583:Cytokinins / Q000096:biosynthesis / Q000378:metabolism* / Q000494:pharmacology; D005308:Fertilizers; D018506:Gene Expression Regulation, Plant; D056626:Inflorescence / Q000187:drug effects / Q000201:enzymology / Q000254:growth & development; D009584:Nitrogen / Q000378:metabolism / Q000494:pharmacology*; D012275:Oryza / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D010641:Phenotype; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology*; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000254:growth & development; D010940:Plant Proteins / Q000235:genetics*; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology / Q000254:growth & development
chemical_list: D003583:Cytokinins; D005308:Fertilizers; D010937:Plant Growth Regulators; D010940:Plant Proteins; D019883:Alkyl and Aryl Transferases; C024274:adenylate isopentenyltransferase; D009584:Nitrogen