title: Competency for shoot regeneration from Arabidopsis root explants is regulated by DNA methylation.
abstract: Plants exhibit high capacity to regenerate in three alternative pathways: tissue repair, somatic embryogenesis and de novo organogenesis. For most plants, de novo organ initiation can be easily achieved in tissue culture by exposing explants to auxin and/or cytokinin, yet the competence to regenerate varies among species and within tissues from the same plant. In Arabidopsis, root explants incubated directly on cytokinin-rich shoot inducing medium (SIM-direct), are incapable of regenerating shoots, and a pre-incubation step on auxin-rich callus inducing medium (CIM) is required to acquire competency to regenerate on the SIM. However the mechanism underlying competency acquisition still remains elusive. Here we show that the chromomethylase 3 (cmt3) mutant which exhibits significant reduction in CHG methylation, shows high capacity to regenerate on SIM-direct and that regeneration occurs via direct organogenesis. In WT, WUSCHEL (WUS) promoter, an essential gene for shoot formation, is highly methylated, and its expression on SIM requires pre-incubation on CIM. However, in cmt3, WUS expression induced by SIM-direct. We propose that pre-incubation on CIM is required for the re-activation of cell division. Following the transfer of roots to SIM, the intensive cell division activity continues, and in the presence of cytokinin leads to a dilution in DNA methylation that allows certain genes required for shoot regeneration to respond to SIM, thereby advancing shoot formation.
authors.affiliation: The Robert H. Smith Institute of Plant Sciences & Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
authors.forename: Or
authors.initials: O
authors.lastname: Shemer
authors.affiliation: The Robert H. Smith Institute of Plant Sciences & Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
authors.forename: Udi
authors.initials: U
authors.lastname: Landau
authors.affiliation: Instituto de Bioingeniería, Universidad Miguel Hernández, Campus de Elche, 03202 Elche, Spain.
authors.forename: Héctor
authors.initials: H
authors.lastname: Candela
authors.affiliation: Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: Assaf
authors.initials: A
authors.lastname: Zemach
authors.affiliation: The Robert H. Smith Institute of Plant Sciences & Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel. Electronic address: leor.williams@mail.huji.ac.il.
authors.forename: Leor
authors.initials: L
authors.lastname: Eshed Williams
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D003470:Culture Media / Q000494:pharmacology; D019175:DNA Methylation / Q000187:drug effects / Q000235:genetics*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D056726:Genetic Association Studies; D009154:Mutation / Q000235:genetics; D038081:Organogenesis / Q000187:drug effects / Q000235:genetics; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012038:Regeneration / Q000187:drug effects
chemical_list: D029681:Arabidopsis Proteins; D003470:Culture Media
keywords: Callus; Competence acquisition; Pericycle; Regeneration; Shoot organogenesis; Totipotency; WUSCHEL; cmt3