title: Nondestructive analysis of senescence in mesophyll cells by spectral resolution of protein synthesis-dependent pigment metabolism.
abstract: * Over 6 d of dark-induced senescence, leaf segments of wild-type Lolium temulentum lost > 96% chlorophyll a + b; leaves from plants containing a staygreen mutation introgressed from Festuca pratensis, which has a lesion in the senescence-associated fragmentation of pigment-proteolipid complexes, retained over 43% of total chlorophyll over the same period. * Mutant segments preferentially retained thylakoid membrane proteins (exemplified by LHCP II) but lost other cellular proteins at the same rate as wild-type tissue. The protein synthesis inhibitor D-MDMP inhibited chlorophyll degradation and partially prevented protein loss in both genotypes, but tissues treated with the ineffective L-stereoisomer were indistinguishable from water controls. * Principal-components analysis of leaf reflectance spectra distinguished between genotypes, time points and D-MDMP treatments, showing the disruption of pigment metabolism during senescence brought about by the staygreen mutation, by inhibition of protein synthesis and by combinations of the two factors. * The build-up of oxidized, dephytylated and phaeo-derivatives of chl a during senescence of staygreen tissue was prevented by D-MDMP and associated with characteristic difference spectra when senescent mutant tissue was compared with wild-type or inhibitor-treated samples. The suitability of senescence as a subject for systems biology approaches is discussed.
authors.affiliation: Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, Ceredigion SY23 3EB, UK.
authors.forename: Alan
authors.initials: A
authors.lastname: Gay
authors.affiliation: Institute of Biological Sciences, Aberystwyth University, Ceredigion SY23 3DA, UK.
authors.forename: Howard
authors.initials: H
authors.lastname: Thomas
authors.affiliation: Instituto de la Grasa (CSIC), Avda Padre García Tejero 4, Sevilla 41012, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Roca
authors.affiliation: Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, Ceredigion SY23 3EB, UK.
authors.forename: Caron
authors.initials: C
authors.lastname: James
authors.affiliation: Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, Ceredigion SY23 3EB, UK.
authors.forename: Janet
authors.initials: J
authors.lastname: Taylor
authors.affiliation: Department of Computer Science, Aberystwyth University, Ceredigion SY23 3DB, UK.
authors.forename: Jem
authors.initials: J
authors.lastname: Rowland
authors.affiliation: Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, Ceredigion SY23 3EB, UK.
authors.forename: Helen
authors.initials: H
authors.lastname: Ougham
mesh_terms: D016922:Cellular Senescence / Q000187:drug effects / Q000502:physiology*; D002734:Chlorophyll / Q000737:chemistry / Q000378:metabolism*; D000077194:Chlorophyll A; D002851:Chromatography, High Pressure Liquid; D031751:Festuca / Q000235:genetics; D005838:Genotype; D008129:Lolium / Q000166:cytology* / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D010860:Pigments, Biological / Q000737:chemistry / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D025341:Principal Component Analysis; D011422:Propionates / Q000494:pharmacology
chemical_list: D010860:Pigments, Biological; D010940:Plant Proteins; D011422:Propionates; D002734:Chlorophyll; C002167:2-(4-methyl-2,6-dinitroanilino)-N-methylpropionamide; C037184:chlorophyll b; D000077194:Chlorophyll A