This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Web of Science (30) Citing Articles via Google Scholar Google Scholar Articles by Legge, R. L. Articles by Thompson, J. E. Search for Related Content PubMed PubMed Citation Articles by Legge, R. L. Articles by Thompson, J. E. Agricola Articles by Legge, R. L. Articles by Thompson, J. E.

Articles

Differential Effects of Senescence on the Molecular Organization of Membranes in Ripening Tomato Fruit ¹

Department of Biology, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1, Department of Physics, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1, Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1

Changes in the molecular organization of membranes in pericarp cells of ripening tomato fruit were examined by fluorescence depolarization after labeling with fluorescent lipid-soluble probes. The fluorescent labels were partitioned into isolated protoplasts and purified plastids from fruit at various stages of senescence. Values for steady-state anisotropy (r_ss) of 1,6-diphenyl-1,3,5-hexatriene (DPH)-labeled protoplasts rose progressively during the early stages of ripening over a time frame that overlapped the climacteric rise in ethylene production. This can be interpreted as reflecting a decrease in the lipid fluidity of primarily plasma membrane. By contrast, there was no significant change during ripening in r_ss for plastid membranes labeled with DPH, 1-[4-trimethylamino)phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH), and cis- or trans-parinaric acid. Nor was there any change during ripening in the limiting fluorescence anisotropy (r_oo) and order parameter (S) for plastids labeled with DPH or TMA-DPH, parameters that are corrected for any differences in lifetime. Some degree of lifetime heterogeneity, possibly reflecting structurally distinct domains, was discerned in both young and senescent plastids that had been labeled with DPH or TMA-DPH, but this also did not change as ripening progressed. Thus membranes of the pericarp cells sustain different fates as the tomato fruit ripens, implying that there are distinguishable mechanisms of membrane deterioration in senescing tissues.

¹ Supported by grants from the Natural Sciences and Engineering Research Council of Canada to J. E. T. and J. R. L.