An iron-induced nitric oxide burst precedes ubiquitin-dependent protein degradation for Arabidospsis Atfer1 ferritin gene expression.
2006
Arnaud, Nicolas | Murgia, Iréne | Boucerez, Jossia | Briat, Jean-François | Cellier, Françoise | Gaymard, Frédéric | Biochimie et Physiologie Moléculaire des Plantes (BPMP) ; Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro) | Sezione di Fisiologia e Biochimica delle Piante, Dipartimento di Biologia ; Università degli Studi di Milano = University of Milan (UNIMI)
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.
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