Plastid changes during the conversion of chloroplasts to chromoplasts in ripening tomatoes
B Bathgate1, M E Purton, D Grierson
1Department of Physiology and Environmental Science, University of Nottingham, School of Agriculture, Sutton Bonington, LE12 5RD, Loughborough, UK.
Abstract:
Methods were developed for the isolation of plastids from mature green and ripening tomatoes (Lycopersicon esculentum Mill.) and purification by sucrose or Percoll density-gradient centrifugation. Assessment of the purity of preparations involved phase-contrast and electron microscopy, assays for marker enzymes and RNA extraction and analysis. Proteins were extracted from isolated plastids at different ripening stages and separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The profiles obtained from chloroplasts and chromoplasts showed many qualitative and quantitative differences. Labelling of proteins with [(35)S]methionine in vivo showed that there was active protein synthesis throughout ripening, but there was a change in the plastid proteins made as ripening proceeded. The cellular location of synthesis of specific proteins has yet to be established.
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