title: Nitric oxide deficiency accelerates chlorophyll breakdown and stability loss of thylakoid membranes during dark-induced leaf senescence in Arabidopsis.
abstract: Nitric oxide (NO) has been known to preserve the level of chlorophyll (Chl) during leaf senescence. However, the mechanism by which NO regulates Chl breakdown remains unknown. Here we report that NO negatively regulates the activities of Chl catabolic enzymes during dark-induced leaf senescence. The transcriptional levels of the major enzyme genes involving Chl breakdown pathway except for RED CHL CATABOLITE REDUCTASE (RCCR) were dramatically up-regulated during dark-induced Chl degradation in the leaves of Arabidopsis NO-deficient mutant nos1/noa1 that exhibited an early-senescence phenotype. The activity of pheide a oxygenase (PAO) was higher in the dark-induced senescent leaves of nos1/noa1 compared with wild type. Furthermore, the knockout of PAO in nos1/noa1 background led to pheide a accumulation in the double mutant pao1 nos1/noa1, which retained the level of Chl during dark-induced leaf senescence. The accumulated pheide a in darkened leaves of pao1 nos1/noa1 was likely to inhibit the senescence-activated transcriptional levels of Chl catabolic genes as a feed-back inhibitory effect. We also found that NO deficiency led to decrease in the stability of photosynthetic complexes in thylakoid membranes. Importantly, the accumulation of pheide a caused by PAO mutations in combination with NO deficiency had a synergistic effect on the stability loss of thylakoid membrane complexes in the double mutant pao1 nos1/noa1 during dark-induced leaf senescence. Taken together, our findings have demonstrated that NO is a novel negative regulator of Chl catabolic pathway and positively functions in maintaining the stability of thylakoid membranes during leaf senescence.
authors: The National Key Laboratory of Plant Molecular Genetics and National Center for Plant Gene Research (Shanghai), Institute of Plant Physiology & Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, People's Republic of China.
authors: Fang
authors: F
authors: Liu
authors: Fang-Qing
authors: FQ
authors: Guo
mesh_terms: D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D002734:Chlorophyll / Q000031:analogs & derivatives / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure; D003624:Darkness; D015971:Gene Expression Regulation, Enzymologic / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D046529:Microscopy, Electron, Transmission; D009154:Mutation; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism; D010788:Photosynthesis / Q000235:genetics / Q000528:radiation effects; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020524:Thylakoids / Q000378:metabolism* / Q000528:radiation effects; D013997:Time Factors
chemical_list: D051017:Apoptosis Regulatory Proteins; D029681:Arabidopsis Proteins; D002734:Chlorophyll; D009569:Nitric Oxide; D010088:Oxidoreductases; D010105:Oxygenases; C112915:pheide a oxygenase; C521947:NOA1 protein, Arabidopsis; D019001:Nitric Oxide Synthase; C408689:ACD2 protein, Arabidopsis; C032623:pheophorbide a