Journal Article

Nitric Oxide Deficiency Accelerates Chlorophyll Breakdown and Stability Loss of Thylakoid Membranes during Dark-Induced Leaf Senescence in Arabidopsis

Guo, Fang-Qing, Liu, Fang

2013

Overview

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.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Accumulation / Apoptosis / Apoptosis Regulatory Proteins - genetics / Apoptosis Regulatory Proteins - metabolism / Arabidopsis / Arabidopsis - genetics / Arabidopsis - metabolism / Arabidopsis - radiation effects / Arabidopsis Proteins - genetics / Arabidopsis Proteins - metabolism / Arabidopsis thaliana / Biology / Blotting, Western / Breakdown / Chlorophyll / Chlorophyll - analogs & derivatives / Chlorophyll - metabolism / Chloroplasts / Chloroplasts - metabolism / Chloroplasts - radiation effects / Chloroplasts - ultrastructure / Cloning / Darkness / Deficient mutant / Enzymes / Gene expression / Gene Expression Regulation, Enzymologic - radiation effects / Gene Expression Regulation, Plant - radiation effects / Genes / Genetic aspects / Genetic transcription / Genomics / Hormones / Laboratories / Leaves / Membranes / Microscopy, Electron, Transmission / Mutation / Nitric oxide / Nitric Oxide - metabolism / Nitric Oxide Synthase - genetics / Nitric Oxide Synthase - metabolism / Nitric-oxide synthase / Oxidoreductases - genetics / Oxidoreductases - metabolism / Oxygenase / Oxygenases - genetics / Oxygenases - metabolism / Photosynthesis / Photosynthesis - genetics / Photosynthesis - radiation effects / Physiology / Plant Leaves - genetics / Plant Leaves - metabolism / Plant Leaves - radiation effects / Proteins / Reductase / Reverse Transcriptase Polymerase Chain Reaction / Senescence / Stability / Synergistic effect / Thylakoid membranes / Thylakoids - metabolism / Thylakoids - radiation effects / Time Factors / Transcription / Trends