An iron-induced nitric oxide burst precedes ubiquitin-dependent protein degradation for Arabidopsis AtFer1 ferritin gene expression.
Ferritins play an essential role in iron homeostasis by sequestering iron in a bioavailable and non-toxic form. In plants, ferritin mRNAs are highly and quickly accumulated in response to iron overload. Such accumulation leads to a subsequent ferritin protein synthesis and iron storage, thus avoiding oxidative stress to take place. By combining pharmacological and imaging approaches in an Arabidopsis cell culture system, we have identified several elements in the signal transduction pathway leading to the increase of AtFer1 transcript level after iron treatment. Nitric oxide quickly accumulates in the plastids after iron treatment. This compound acts downstream of iron and upstream of a PP2A-type phosphatase to promote an increase of AtFer1 mRNA level. The AtFer1 gene transcription has been previously shown to be repressed under low iron conditions with the involvement of the cis-acting element iron-dependent regulatory sequence identified within the AtFer1 promoter sequence. We show here that the repressor is unlikely a transcription factor directly bound to the iron-dependent regulatory sequence; such a repressor is ubiquitinated upon iron treatment and subsequently degraded through a 26 S proteasome-dependent pathway.
Arnaud
Nicolas
N
Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, UMR 5004 Agro-M/CNRS/INRA/UMII, Bat 7, 2 place Viala, 34060 Montpellier Cedex 1, France.
Murgia
Irene
I
Boucherez
Jossia
J
Briat
Jean-François
JF
Cellier
Françoise
F
Gaymard
Frédéric
F
D017360:Arabidopsis / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D005293:Ferritins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000378:metabolism; D007501:Iron / Q000737:chemistry* / Q000502:physiology; D035925:Iron-Regulatory Proteins / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D018087:Plastids / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics; D012097:Repressor Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D025801:Ubiquitin / Q000502:physiology*
D035925:Iron-Regulatory Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D025801:Ubiquitin; D009569:Nitric Oxide; D005293:Ferritins; D006861:Hydrogen Peroxide; D007501:Iron; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease