title: RcRR1, a Rosa canina type-A response regulator gene, is involved in cytokinin-modulated rhizoid organogenesis.
abstract: In vitro, a new protocol of plant regeneration in rose was achieved via protocorm-like bodies (PLBs) induced from the root-like organs named rhizoids that developed from leaf explants. The development of rhizoids is a critical stage for efficient regeneration, which is triggered by exogenous auxin. However, the role of cytokinin in the control of organogenesis in rose is as yet uncharacterized. The aim of this study was to elucidate the molecular mechanism of cytokinin-modulated rhizoid formation in Rosa canina. Here, we found that cytokinin is a key regulator in the formation of rhizoids. Treatment with cytokinin reduced callus activity and significantly inhibited rhizoid formation in Rosa canina. We further isolated the full-length cDNA of a type-A response regulator gene of cytokinin signaling, RcRR1, from which the deduced amino acid sequence contained the conserved DDK motif. Gene expression analysis revealed that RcRR1 was differentially expressed during rhizoid formation and its expression level was rapidly up-regulated by cytokinin. In addition, the functionality of RcRR1 was tested in Arabidopsis. RcRR1 was found to be localized to the nucleus in GFP-RcRR1 transgenic plants and overexpression of RcRR1 resulted in increased primary root length and lateral root density. More importantly, RcRR1 overexpression transgenic plants also showed reduced sensitivity to cytokinin during root growth; auxin distribution and the expression of auxin efflux carriers PIN genes were altered in RcRR1 overexpression plants. Taken together, these results demonstrate that RcRR1 is a functional type-A response regulator which is involved in cytokinin-regulated rhizoid formation in Rosa canina.
authors.affiliation: Department of Ornamental Horticulture and Landscape Architecture, China Agricultural University, Beijing, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Gao
authors.forename: Lusheng
authors.initials: L
authors.lastname: Fan
authors.forename: Xingxing
authors.initials: X
authors.lastname: Li
authors.forename: Huifang
authors.initials: H
authors.lastname: Yang
authors.forename: Fengluan
authors.initials: F
authors.lastname: Liu
authors.forename: Ling
authors.initials: L
authors.lastname: Wang
authors.forename: Lin
authors.initials: L
authors.lastname: Xi
authors.forename: Nan
authors.initials: N
authors.lastname: Ma
authors.forename: Liangjun
authors.initials: L
authors.lastname: Zhao
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D003583:Cytokinins / Q000494:pharmacology*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D007210:Indoleacetic Acids / Q000494:pharmacology; D008969:Molecular Sequence Data; D038081:Organogenesis / Q000187:drug effects* / Q000235:genetics*; D010641:Phenotype; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000494:pharmacology*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development; D030821:Plants, Genetically Modified; D021381:Protein Transport; D027826:Rosa / Q000196:embryology* / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D003583:Cytokinins; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D010940:Plant Proteins