title: Stay-green protein, defective in Mendel's green cotyledon mutant, acts independent and upstream of pheophorbide a oxygenase in the chlorophyll catabolic pathway.
abstract: Type C stay-green mutants are defined as being defective in the pathway of chlorophyll breakdown, which involves pheophorbide a oxygenase (PAO), required for loss of green color. By analyzing senescence parameters, such as protein degradation, expression of senescence-associated genes and loss of photosynthetic capacity, we demonstrate that JI2775, the green cotyledon (i) pea line used by Gregor Mendel to establish the law of genetics, is a true type C stay-green mutant. STAY-GREEN (SGR) had earlier been shown to map to the I locus. The defect in JI2775 is due to both reduced expression of SGR and loss of SGR protein function. Regulation of PAO through SGR had been proposed. By determining PAO protein abundance and activity, we show that PAO is unaffected in JI2775. Furthermore we show that pheophorbide a accumulation in the mutant is independent of PAO. When silencing SGR expression in Arabidopsis pao1 mutant, both pheophorbide a accumulation and cell death phenotype, typical features of pao1, are lost. These results confirm that SGR function within the chlorophyll catabolic pathway is independent and upstream of PAO.
authors.affiliation: Institute of Plant Biology, University of Zurich, Zurich, Switzerland.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Aubry
authors.forename: Jan
authors.initials: J
authors.lastname: Mani
authors.forename: Stefan
authors.initials: S
authors.lastname: Hörtensteiner
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D016922:Cellular Senescence; D002734:Chlorophyll / Q000378:metabolism*; D002735:Chlorophyllides / Q000378:metabolism; D003001:Cloning, Molecular; D018548:Cotyledon / Q000201:enzymology* / Q000235:genetics; D017931:DNA Primers; D010105:Oxygenases / Q000235:genetics* / Q000378:metabolism*; D018532:Pisum sativum / Q000201:enzymology* / Q000235:genetics*; D018515:Plant Leaves / Q000201:enzymology / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D002735:Chlorophyllides; D017931:DNA Primers; D010940:Plant Proteins; D002734:Chlorophyll; D002245:Carbon Dioxide; C034388:chlorophyllide a; D010105:Oxygenases; C112915:pheide a oxygenase