title: Initiation of a legume nodule with an indeterminate meristem involves proliferating host cells that harbour infection threads.
abstract: A comparative analysis of nodule morphogenesis was carried out for three symbiotically defective pea (Pisum sativum) mutants that show abnormalities in nodule development.In the wild-type lines, resumption of cell proliferation in the pericycle and inner cortex results in the development of a nodule primordium, within which are found proliferating cells that harbour infection threads. However, this class of cell is not observed in the mutants RisFixA (sym41) and SGEFix–-2 (sym33) where nodule development is arrested at the point of formation of the apical nodule meristem. Itis proposed that the presence of proliferating cells harbouring infection threads is a prerequisite for normal formation of the nodule meristem.In mutant SGEFix–-1 (sym40), nodule development does not differ from that of wild-type plants in the early stages but is blocked at the stage after nodule meristem persistence. A scheme is proposed for the sequential functioning of pea symbiotic genes Sym33, Sym40 and Sym41 in the programme of nodule development.
authors.affiliation: All-Russia Research Institute for Agricultural Microbiology, Laboratory of Genetics of Plant-Microbe Interactions, Podbelsky chaussee 3, 196608, Pushkin 8, St Petersburg, Russia.
authors.forename: Vera A
authors.initials: VA
authors.lastname: Voroshilova
authors.affiliation: All-Russia Research Institute for Agricultural Microbiology, Laboratory of Genetics of Plant-Microbe Interactions, Podbelsky chaussee 3, 196608, Pushkin 8, St Petersburg, Russia.|Laboratory of Anatomy and Morphology, Komarov Botanical Institute, Russian Academy of Sciences, Prof. Popov Str. 2, 197376, St Petersburg, Russia.
authors.forename: Kirill N
authors.initials: KN
authors.lastname: Demchenko
authors.affiliation: John Innes Centre, Norwich NR4 7UH, UK.
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Brewin
authors.affiliation: All-Russia Research Institute for Agricultural Microbiology, Laboratory of Genetics of Plant-Microbe Interactions, Podbelsky chaussee 3, 196608, Pushkin 8, St Petersburg, Russia.
authors.forename: Alexey Y
authors.initials: AY
authors.lastname: Borisov
authors.affiliation: All-Russia Research Institute for Agricultural Microbiology, Laboratory of Genetics of Plant-Microbe Interactions, Podbelsky chaussee 3, 196608, Pushkin 8, St Petersburg, Russia.
authors.forename: Igor A
authors.initials: IA
authors.lastname: Tikhonovich
mesh_terms: D049109:Cell Proliferation; D018519:Meristem / Q000166:cytology / Q000382:microbiology; D009154:Mutation; D018532:Pisum sativum / Q000235:genetics / Q000382:microbiology* / Q000502:physiology; D012231:Rhizobium / Q000502:physiology; D053204:Root Nodules, Plant / Q000235:genetics / Q000382:microbiology* / Q000502:physiology