title: Developmental programmed cell death during asymmetric microsporogenesis in holocentric species of Rhynchospora (Cyperaceae).
abstract: Members of the Cyperaceae family exhibit an asymmetric microsporogenesis that results in the degeneration of three out of four meiotic products. Efforts have been made previously to describe the resulting structure, named the pseudomonad, but mechanisms concerning the establishment of cell domains, nuclear development, and programmed cell death are largely unknown. Using the Rhynchospora genus as a model, evidence for cell asymmetry, cytoplasmic isolation, and programmed cell death was obtained by a combination of electron microscopic, cytochemical, immunocytochemical, in situ hybridization, and flow cytometric methods. Degenerative cells were identified at the abaxial region, with the cytoskeleton marking their delimitation from the functional domain after meiosis. After attempting to initiate cell division with an unreplicated genome and abnormal spindle assembly, these cells exhibited a gradual process of cytoplasmic contraction associated with hypermethylation of cytosines and differential loss of DNA. These results indicate that the asymmetric tetrad establishes a functional cell, where one nucleus is preferentially selected to survive. Degenerative haploid cells are then eliminated in a multistep process associated with mitotic disorder, non-random elimination of repetitive DNA, vacuolar cell death, and DNA fragmentation.
authors: Laboratory of Cytogenetics and Plant Diversity, Department of General Biology, Center of Biological Sciences, State University of Londrina, Londrina 86057-970, Paraná, Brazil.
authors: Danilo M
authors: DM
authors: Rocha
authors: Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Federal University of Pernambuco, Recife, Brazil.
authors: André
authors: A
authors: Marques
authors: Laboratory of Electron Microscopy and Microanalysis, Pro-PPG, State University of Londrina, 86051990, Londrina, Brazil.
authors: Celia G T J
authors: CG
authors: Andrade
authors: Institut de Recherche pour le Développement (IRD), UMR IPME, BP 64501, 34394, Montpellier Cedex, France.
authors: Romain
authors: R
authors: Guyot
authors: Department of Genetics, University of Georgia, Athens, GA 30602, USA.
authors: Srinivasa R
authors: SR
authors: Chaluvadi
authors: Laboratory of Plant Cytogenetics and Evolution, Department of Botany, Federal University of Pernambuco, Recife, Brazil.
authors: Andrea
authors: A
authors: Pedrosa-Harand
authors: Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) Gatersleben, D-06466 Stadt Seeland, Germany.
authors: Andreas
authors: A
authors: Houben
authors: Department of Genetics, University of Georgia, Athens, GA 30602, USA.
authors: Jeffrey L
authors: JL
authors: Bennetzen
authors: Laboratory of Cytogenetics and Plant Diversity, Department of General Biology, Center of Biological Sciences, State University of Londrina, Londrina 86057-970, Paraná, Brazil andrevanzela@uel.br.
authors: André L L
authors: AL
authors: Vanzela
mesh_terms: D016923:Cell Death / Q000502:physiology*; D002455:Cell Division / Q000502:physiology; D029785:Cyperaceae / Q000502:physiology* / Q000648:ultrastructure; D003593:Cytoplasm / Q000502:physiology; D003599:Cytoskeleton / Q000502:physiology; D056130:Gametogenesis, Plant / Q000502:physiology*; D017403:In Situ Hybridization; D008540:Meiosis / Q000502:physiology; D008854:Microscopy, Electron
keywords: Asymmetric cell plate; electron microscopy; holocentromeres; meiotic drive; mitotic disorder; pollen development; vacuolar cell death.