title: Functional characterization and hormonal regulation of the PHEOPHYTINASE gene LpPPH controlling leaf senescence in perennial ryegrass.
abstract: Chlorophyll (Chl) degradation occurs naturally during leaf maturation and senescence, and can be induced by stresses, both processes involving the regulation of plant hormones. The objective of this study was to determine the functional roles and hormonal regulation of a gene encoding pheophytin pheophorbide hydrolyase (PPH) that catabolizes Chl degradation during leaf senescence in perennial grass species. A PPH gene, LpPPH, was cloned from perennial ryegrass (Lolium perenne L.). LpPPH was localized in the chloroplast. Overexpressing LpPPH accelerated Chl degradation in wild tobacco, and rescued the stay-green phenotype of the Arabidopsis pph null mutant. The expression level of LpPPH was positively related to the extent of leaf senescence. Exogenous application of abscisic acid (ABA) and ethephon (an ethylene-releasing agent) accelerated the decline in Chl content in leaves of perennial ryegrass, whereas cytokinin (CK) and aminoethoxyvinylglycine (AVG; an ethylene biosynthesis inhibitor) treatments suppressed leaf senescence, corresponding to the up- or down-regulation of LpPPH expression. The promoters of five orthologous PPH genes were predicted to share conserved cis-elements potentially recognized by transcription factors in the ABA and CK pathways. Taken together, the results suggested that LpPPH-mediated Chl breakdown could be regulated positively by ABA and ethylene, and negatively by CK, and LpPPH could be a direct downstream target gene of transcription factors in the ABA and CK signaling pathways.
authors.affiliation: College of Agro-grassland Science, Nanjing Agricultural University, Nanjing, 210095, PR China Department of Plant Biology and Pathology, Rutgers, the State University of New Jersey, New Brunswick, NJ 08901, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: College of Agro-grassland Science, Nanjing Agricultural University, Nanjing, 210095, PR China.
authors.forename: Guohui
authors.initials: G
authors.lastname: Yu
authors.affiliation: College of Agro-grassland Science, Nanjing Agricultural University, Nanjing, 210095, PR China.
authors.forename: Wuwu
authors.initials: W
authors.lastname: Wen
authors.affiliation: College of Agro-grassland Science, Nanjing Agricultural University, Nanjing, 210095, PR China Department of Plant Biology and Pathology, Rutgers, the State University of New Jersey, New Brunswick, NJ 08901, USA.
authors.forename: Xiqing
authors.initials: X
authors.lastname: Ma
authors.affiliation: College of Agro-grassland Science, Nanjing Agricultural University, Nanjing, 210095, PR China binxu@njau.edu.cn huang@aesop.rutgers.
authors.forename: Bin
authors.initials: B
authors.lastname: Xu
authors.affiliation: Department of Plant Biology and Pathology, Rutgers, the State University of New Jersey, New Brunswick, NJ 08901, USA binxu@njau.edu.cn huang@aesop.rutgers.
authors.forename: Bingru
authors.initials: B
authors.lastname: Huang
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism / Q000494:pharmacology; D000595:Amino Acid Sequence; D002736:Chloroplasts / Q000187:drug effects / Q000201:enzymology; D003001:Cloning, Molecular; D017124:Conserved Sequence; D003583:Cytokinins / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D005816:Genetic Complementation Test; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D008129:Lolium / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009943:Organophosphorus Compounds / Q000494:pharmacology; D010641:Phenotype; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000494:pharmacology*; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D003583:Cytokinins; D009943:Organophosphorus Compounds; D010937:Plant Growth Regulators; D010940:Plant Proteins; D012333:RNA, Messenger; D000040:Abscisic Acid; C088137:aminoethoxyvinylglycine; D005998:Glycine; C005073:ethephon
keywords: ABA; Chl degradation; PPH.; cytokinin; ethylene; leaf senescence