title: FINE CULM1 (FC1) works downstream of strigolactones to inhibit the outgrowth of axillary buds in rice.
abstract: Recent studies of highly branched mutants of pea, Arabidopsis and rice have demonstrated that strigolactones (SLs) act as hormones that inhibit shoot branching. The identification of genes that work downstream of SLs is required for a better understanding of how SLs control the growth of axillary buds. We found that the increased tillering phenotype of fine culm1 (fc1) mutants of rice is not rescued by the application of 1 microM GR24, a synthetic SL analog. Treatment with a high concentration of GR24 (10 microM) causes suppression of tiller growth in wild-type plants, but is not effective on fc1 mutants, implying that proper FC1 functioning is required for SLs to inhibit bud growth. Overexpression of FC1 partially rescued d3-2 defects in the tiller growth and plant height. An in situ hybridization analysis showed that FC1 mRNA accumulates in axillary buds, the shoot apical meristem, young leaves, vascular tissues and the tips of crown roots. FC1 mRNA expression was not significantly affected by GR24, suggesting that transcriptional induction may not be the mechanism by which SLs affect FC1 functioning. On the other hand, the expression level of FC1 is negatively regulated by cytokinin treatment. We propose that FC1 acts as an integrator of multiple signaling pathways and is essential to the fine-tuning of shoot branching in rice.
authors.affiliation: Graduate School of Agriculture and Life Sciences, University of Tokyo, Yayoi, Bunkyo, Tokyo, 113-8657 Japan.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Minakuchi
authors.forename: Hiromu
authors.initials: H
authors.lastname: Kameoka
authors.forename: Naoko
authors.initials: N
authors.lastname: Yasuno
authors.forename: Mikihisa
authors.initials: M
authors.lastname: Umehara
authors.forename: Le
authors.initials: L
authors.lastname: Luo
authors.forename: Kaoru
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hanada
authors.forename: Kotomi
authors.initials: K
authors.lastname: Ueno
authors.forename: Tadao
authors.initials: T
authors.lastname: Asami
authors.forename: Shinjiro
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: Junko
authors.initials: J
authors.lastname: Kyozuka
mesh_terms: D003583:Cytokinins / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D007783:Lactones / Q000378:metabolism*; D009154:Mutation; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018520:Plant Shoots / Q000254:growth & development*; D012333:RNA, Messenger / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics
chemical_list: D003583:Cytokinins; D007783:Lactones; D010937:Plant Growth Regulators; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant