The control of chlorophyll catabolism and the status of yellowing as a biomarker of leaf senescence

Abstract

Ougham, H. J., Hortensteiner, S., Armstead, I. P., Donnison, I. S., King, I. P., Thomas, Howard, Mur, L. A. J. (2008). The control of chlorophyll catabolism and the status of yellowing as a biomarker of leaf senescence. Plant Biology, 10, (Supplement 1), pp. 4-14 IMPF: 01.94 RONO: 1310 3001The pathway of chlorophyll catabolism during leaf senescence is known in a fair amount of biochemical and cell biological detail. In the last few years, genes encoding a number of the catabolic enzymes have been characterized, including the key ring-opening activities, phaeophorbide a oxygenase (PaO) and red chlorophyll catabolite reductase (RCCR). Recently, a gene that modulates disassembly of chlorophyll?protein complexes and activation of pigment ring-opening has been isolated by comparative mapping in monocot species, positional cloning exploiting rice genomics resources and functional testing in Arabidopsis. The corresponding gene in pea has been identified as Mendel's I locus (green/yellow cotyledons). Mutations in this and other chlorophyll catabolic genes have significant consequences, both for the course of leaf senescence and senescence-like stress responses, notably hypersensitivity to pathogen challenge. Loss of chlorophyll can occur via routes other than the PaO/RCCR pathway, resulting in changes that superficially resemble senescence. Such 'pseudosenescence' responses tend to be pathological rather than physiological and may differ from senescence in fundamental aspects of biochemistry and regulation.Peer reviewe

Physiology and biochemistry of leaf bleaching in prematurely aging maple (Acer saccharinum L.) trees: I. Hydrogen peroxide level, antioxidative responses and photosynthetic pigments

“…A lower Fv/Fm value in bleached leaves indicates a stress situation as well as declined photosynthesis. The lowering of photosynthetic parameters was previously reported in leaves of maize, ginkgo and birch that also contained higher level of H 2 O 2 (FOYER et al 2002, KUKAVICA and VELJOVIC-JOVANOVIC 2004, OUGHAM et al 2008). …”

Metabolic Regulation of Leaf Senescence in Sunflower (Helianthus annuus L.) Plants

“…Also, the protein content in senescing sunflower leaves was found to drop earlier in nitrogen-deficient plants than in high-nitrogen plants (Agüera et al, 2010). Changes in photosynthetic pigment contents also indicate progress of leaf senescence (Yoo et al, 2003;Guo & Gan, 2005;Ougham et al, 2008). The chlorophyll breakdown pathways operating during leaf senescence are well-known and require pigment degradation and avoiding photodamage in order to maintain the ability to export released nutrients to other plant parts (Hörtensteiner, 2006;Ougham et al, 2008).…”

“…Changes in photosynthetic pigment contents also indicate progress of leaf senescence (Yoo et al, 2003;Guo & Gan, 2005;Ougham et al, 2008). The chlorophyll breakdown pathways operating during leaf senescence are well-known and require pigment degradation and avoiding photodamage in order to maintain the ability to export released nutrients to other plant parts (Hörtensteiner, 2006;Ougham et al, 2008). Chlorophylls in sunflower plants are more susceptible to degradation than are carotenoids during leaf senescence, and both total chlorophyll and carotenoid contents are high in young and mature leaves, their levels peaking at 22 days and decreasing afterwards during senescence (Fig.…”

Growth, morphological and photosynthetic characteristics, antioxidant capacity, biomass yield and water use efficiency of Gynura bicolor DC exposed to super-elevated CO2

“…The redistribution of nitrogen from chlorophyll binding proteins is considered to be the main cause of chlorophyll degradation [62]. Other explanation however cannot be excluded, the negative CO 2 effect on chlorophyll content might be explained with the hypothesis that super-elevated [CO 2 ] induced a higher starch accumulation that disrupts chloroplasts and increases chlorophyll degradation or decreases chlorophyll synthesis [47,49].…”