Programmed cell death in quinoa leaves

LOPEZ FERNANDEZ MP; MALDONADO S; BURRIEZA HP

Salvador, BA

Congreso; congreso latinoamericano de botânica; 2014

A delay in the onset of leaf senescence has an important impact on the grain yield due to the maintenance of photosynthetically active leaf area during the reproductive stage; also impacts in leaf crop performance because prevents early foliar degradation. Leaf senescence involves a cell death program that is controlled by age under the influence of other endogenous and environmental factors. Here we investigated programmed cell death (PCD) hallmarks during leaf senescence in Chenopodium quinoa Willd., using diverse but complementary methods: In addition to structural studies using light microscopy and transmission electron microscopy (TEM), a terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling (TUNEL) assay is carried out to determine DNA fragmentation and; the participation of nucleases in nucleus dismantling is evaluated by electrophoresis through development. Additionally, to detect RuBisCO degradation we use immunological techniques such as western blot and in situ immunolocalization assays. Finally, flow cytometry is used to determine change of ploidy level during development. We detected distinctive structural and biochemical changes progressively through development: in the chloroplasts, grana disorganization, chlorophyll loss, formation of plastoglobuli, and RuBisCO degradation; nuclei and mitochondria remain intact until the last stages of senescence where DNA fragmentation is detected; in the latest senescence stages, vacuolar collapse, chromatin condensation, endopoliploidy, and finally, disintegration of tonoplast, plasmalemma,and nuclear membranes. The increase of ploidy level accompanying the chlorophyll loss is involved in the process of nutrient relocation from senescent leaves to meristems and to developing fruits and seeds. We consider that these results provide novel and important information for the studies on leaf senescence.