title: Cellular and molecular aspects of quinoa leaf senescence.
abstract: During leaf senescence, degradation of chloroplasts precede to changes in nuclei and other cytoplasmic organelles, RuBisCO stability is progressively lost, grana lose their structure, plastidial DNA becomes distorted and degraded, the number of plastoglobuli increases and abundant senescence-associated vesicles containing electronically dense particles emerge from chloroplasts pouring their content into the central vacuole. This study examines quinoa leaf tissues during development and senescence using a range of well-established markers of programmed cell death (PCD), including: morphological changes in nuclei and chloroplasts, degradation of RuBisCO, changes in chlorophyll content, DNA degradation, variations in ploidy levels, and changes in nuclease profiles. TUNEL reaction and DNA electrophoresis demonstrated that DNA fragmentation in nuclei occurs at early senescence, which correlates with induction of specific nucleases. During senescence, metabolic activity is high and nuclei endoreduplicate, peaking at 4C. At this time, TEM images showed some healthy nuclei with condensed chromatin and nucleoli. We have found that DNA fragmentation, induction of senescence-associated nucleases and endoreduplication take place during leaf senescence. This provides a starting point for further research aiming to identify key genes involved in the senescence of quinoa leaves.
authors.affiliation: IBBEA (Instituto de Biodiversidad y Biología Experimental y Aplicada), CONICET (Consejo Nacional de Investigaciones Científicas Técnicas). Argentina; DBBE (Departamento de Biodiversidad y Biología Experimental), FCEN (Facultad de Ciencias Exactas y Naturales), UBA (Universidad de Buenos Aires), Int. Güiraldes 2160, Ciudad Universitaria, C1428EGA, Argentina.
authors.forename: María Paula
authors.initials: MP
authors.lastname: López-Fernández
authors.affiliation: IBBEA (Instituto de Biodiversidad y Biología Experimental y Aplicada), CONICET (Consejo Nacional de Investigaciones Científicas Técnicas). Argentina; DBBE (Departamento de Biodiversidad y Biología Experimental), FCEN (Facultad de Ciencias Exactas y Naturales), UBA (Universidad de Buenos Aires), Int. Güiraldes 2160, Ciudad Universitaria, C1428EGA, Argentina.
authors.forename: Hernán Pablo
authors.initials: HP
authors.lastname: Burrieza
authors.affiliation: DBBE (Departamento de Biodiversidad y Biología Experimental), FCEN (Facultad de Ciencias Exactas y Naturales), UBA (Universidad de Buenos Aires), Int. Güiraldes 2160, Ciudad Universitaria, C1428EGA, Argentina.
authors.forename: Axel Joel
authors.initials: AJ
authors.lastname: Rizzo
authors.affiliation: IBBEA (Instituto de Biodiversidad y Biología Experimental y Aplicada), CONICET (Consejo Nacional de Investigaciones Científicas Técnicas). Argentina.
authors.forename: Leandro Julián
authors.initials: LJ
authors.lastname: Martínez-Tosar
authors.affiliation: IBBEA (Instituto de Biodiversidad y Biología Experimental y Aplicada), CONICET (Consejo Nacional de Investigaciones Científicas Técnicas). Argentina; DBBE (Departamento de Biodiversidad y Biología Experimental), FCEN (Facultad de Ciencias Exactas y Naturales), UBA (Universidad de Buenos Aires), Int. Güiraldes 2160, Ciudad Universitaria, C1428EGA, Argentina. Electronic address: saram@bg.fcen.uba.ar.
authors.forename: Sara
authors.initials: S
authors.lastname: Maldonado
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure; D027465:Chenopodium quinoa / Q000166:cytology* / Q000235:genetics / Q000254:growth & development* / Q000648:ultrastructure; D002736:Chloroplasts / Q000378:metabolism / Q000648:ultrastructure; D053938:DNA Fragmentation; D003851:Deoxyribonucleases / Q000378:metabolism; D005434:Flow Cytometry; D018515:Plant Leaves / Q000166:cytology* / Q000235:genetics / Q000254:growth & development* / Q000648:ultrastructure; D011003:Ploidies; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism
chemical_list: D003851:Deoxyribonucleases; D012273:Ribulose-Bisphosphate Carboxylase
keywords: DNA fragmentation; Endoreduplication; Leaf senescence; Nucleases; Quinoa