Leaf Senescence in a Nonyellowing Mutant of Festuca pratensis

Abstract

In a mutant genotype of Festuca pratensis Huds., net degradation of a number of thylakoid membrane proteins during senescence is impaired. Previous studies have suggested that the highly hydrophobic intrinsic chlorophyll-binding proteins were the definitive subjects of the metabolic lesion. In the present study we find that cytochrome f, as determined by haem-staining, Western blotting, enzyme-linked immunosorbent assay, and immunogold electron microscopy, is also abnormally stable in the mutant. The structural feature common to all the proteins in the mutant so far recognized to be abnormally stable is possession of a tetrapyrrole prosthetic group. It is suggested that degradation of chlorophyll and haem may regulate degradation of the associated apoproteins, and hence has an important role to play in membrane protein turnover and in mobilisation of amino acids during chloroplast disassembly.In most graminaceous species, each leaf has only a limited life span. During vegetative growth the older leaves at the base tend to senesce as the shoot extends. One of the most striking changes seen in senescing leaves is the appearance of a yellow coloration as Chl is degraded. A mutant of Festuca pratensis exists in which the syndrome of leaf senescence is no longer accompanied by Chl breakdown (25). The nonyellowing character is associated with a marked structural stability of thylakoids during senescence. The mutant genotype therefore presents a unique opportunity to study the processes responsible for the degradation of chloroplast membranes. Previous investigations have focused on the proteins ofPSII ( 11). Intrinsic components such as the nuclear-encoded LHCP-22 and the chloroplast-encoded Dl protein were found to be retained by the mutant during senescence of detached leaves. By contrast, PSII proteins extrinsic to the membrane, such as the 33-kD

Senescence of rice leaves XXXI. Changes of chlorophyll, protein, and polyamine contents and ethylene production during senescence of a chlorophyll-deficient mutant

“…Leaf senescence is a syndrome, comprising a number of biochemical and physiological changes. To date, the nonyellowing genotype of meadow fescue is the only mutant used to study leaf senescence (Emyr Davies et al 1990). LT-8 is a chlorophyll-deficient mutant of rice derived from Norin no.…”

Stay‐green genotypes of Phaseolus vulgaris L.: chloroplast proteins and chlorophyll catabolites during foliar senescence

“….. u i-/u j T fl T^U inoT metabolism (Harwood, Jones & 1 homas, 1982; Mutants have become important subjects for re 19S8a), membrane protein breaksearch on the genetic and biochemical regulation of down (Hilditcb et aL, 1989;Davies et aL, 19906) and leaf senescence (Thomas & Smart, 1993). The most gene expression (Thomas, Ougham & Davies, 1992).…”

Chlorophyll Biosynthetic Reactions during Senescence of Excised Barley (Hordeum vulgare L. cv IB 65) Leaves

“…fluorescent or nonfluorescent; (b) elution profile of the catabolites on the reverse-phase HPLC due to changing polarity; and (c) plant species concemed. Senescence-induced differential gene expression and tumover of various proteins and Chlbinding apoproteins associated with thylakoid membranes have been demonstrated in a normal cultivar and a nonyellowing mutant of Festuca pratensis (Hilditch et al, 1989;Davies et al, 1990;Nock et al, 1992;Thomas et al, 1992).…”