Mutation of the Arabidopsis NAC016 transcription factor delays leaf senescence.
The highly ordered process of senescence forms the final stage of leaf development; a large set of senescence-associated genes (SAGs) execute this orderly dismantling of the photosynthetic apparatus and remobilization of cellular components. A number of transcription factors (TFs) modulate SAG expression to promote or delay senescence. Here we show that NAC016, the previously uncharacterized senescence-associated NAM/ATAF1/2/CUC2 (senNAC) TF in Arabidopsis thaliana, promotes senescence. Leaves of nac016 mutants remained green under senescence-inducing conditions, and leaves of NAC016-overexpressing (NAC016-OX) plants senesced early. Under dark-induced senescence (DIS) conditions, nac016 mutants had low ion leakage, and retained the proper balance of photosystem proteins and normal grana thylakoid shape much longer than wild-type plants, suggesting that nac016 acts as a functional stay-green type senescence mutant. Under DIS conditions, SAGs (NYC1, PPH, SGR1/NYE1 and WRKY22), including senNACs (JUB1, NAP, ORE1, ORS1 and VNI2), were down-regulated in nac016 mutants and up-regulated in NAC016-OX plants. In addition to its role in senescence, NAC016 also affects abiotic stress. Under salt and oxidative stress conditions, NAC016 expression rapidly increased in developing leaves, possibly to promote senescence. Indeed, under the stress conditions, nac016 mutants stayed green and NAC016-OX plants senesced rapidly. To identify direct targets of the NAC016 TF in the regulation of leaf senescence, we conducted yeast one-hybrid assays, which strongly suggested that NAC016 binds to the promoters of NAP and ORS1. Based on these results, we propose that NAC016 regulatory mechanisms promoting leaf senescence exhibit cross-talk with the salt and oxidative stress-responsive signaling pathways.
Department of Plant Science, Plant Genomics and Breeding Institute, and Research Institute for Agriculture and Life Sciences, Seoul National University, Seoul, 151-921, Republic of Korea.
Ye-Sol
YS
Kim
Yasuhito
Y
Sakuraba
Su-Hyun
SH
Han
Soo-Cheul
SC
Yoo
Nam-Chon
NC
Paek
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D029681:Arabidopsis Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D003624:Darkness; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D006861:Hydrogen Peroxide / Q000494:pharmacology; D015151:Immunoblotting; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D009154:Mutation; D016877:Oxidants / Q000494:pharmacology; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000494:pharmacology; D018515:Plant Leaves / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D030821:Plants, Genetically Modified; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D012965:Sodium Chloride / Q000494:pharmacology; D020524:Thylakoids / Q000187:drug effects / Q000528:radiation effects / Q000648:ultrastructure; D014157:Transcription Factors / Q000145:classification / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
D029681:Arabidopsis Proteins; C588366:NAC016 protein, Arabidopsis; C110811:NAP protein, Arabidopsis; D016877:Oxidants; D010937:Plant Growth Regulators; D014157:Transcription Factors; D012965:Sodium Chloride; D006861:Hydrogen Peroxide
Arabidopsis; Leaf senescence; NAC016; Oxidative stress; Salt stress; Stay-green