title: Lotus japonicus SUNERGOS1 encodes a predicted subunit A of a DNA topoisomerase VI that is required for nodule differentiation and accommodation of rhizobial infection.
abstract: A symbiotic mutant of Lotus japonicus, called sunergos1-1 (suner1-1), originated from a har1-1 suppressor screen. suner1-1 supports epidermal infection by Mesorhizobium loti and initiates cell divisions for organogenesis of nodule primordia. However, these processes appear to be temporarily stalled early during symbiotic interaction, leading to a low nodule number phenotype. This defect is ephemeral and near wild-type nodule numbers are reached by suner1-1 at a later point after infection. Using an approach that combined map-based cloning and next-generation sequencing we have identified the causative mutation and show that the suner1-1 phenotype is determined by a weak recessive allele, with the corresponding wild-type SUNER1 locus encoding a predicted subunit A of a DNA topoisomerase VI. Our data suggest that at least one function of SUNER1 during symbiosis is to participate in endoreduplication, which is an essential step during normal differentiation of functional, nitrogen-fixing nodules.
authors.affiliation: Agriculture and Agri-Food Canada, Southern Crop Protection and Food Research Centre, London, ON, N5V 4T3, Canada; Department of Biology, University of Western Ontario, London, ON, N6A 5B7, Canada.
authors.forename: Hwi Joong
authors.initials: HJ
authors.lastname: Yoon
authors.forename: Md Shakhawat
authors.initials: MS
authors.lastname: Hossain
authors.forename: Mark
authors.initials: M
authors.lastname: Held
authors.forename: Hongwei
authors.initials: H
authors.lastname: Hou
authors.forename: Marilyn
authors.initials: M
authors.lastname: Kehl
authors.forename: Alexandre
authors.initials: A
authors.lastname: Tromas
authors.forename: Shusei
authors.initials: S
authors.lastname: Sato
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tabata
authors.forename: Stig Uggerhøj
authors.initials: SU
authors.lastname: Andersen
authors.forename: Jens
authors.initials: J
authors.lastname: Stougaard
authors.forename: Loretta
authors.initials: L
authors.lastname: Ross
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Szczyglowski
mesh_terms: D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism*; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D000070116:Lotus / Q000201:enzymology*; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology; D012231:Rhizobium / Q000502:physiology*; D053204:Root Nodules, Plant / Q000235:genetics / Q000378:metabolism*; D013559:Symbiosis / Q000235:genetics / Q000502:physiology*
chemical_list: D019843:Archaeal Proteins; D010940:Plant Proteins; C105141:DNA topoisomerase VI; D004250:DNA Topoisomerases, Type II
keywords: Lotus japonicus; endocycle; legumes; symbiosis; topoisomerase