CHARACTERIZATION OF A FERRITIN MESSENGER-RNA FROM ARABIDOPSIS-THALIANA ACCUMULATED IN RESPONSE TO IRON THROUGH AN OXIDATIVE PATHWAY INDEPENDENT OF ABSCISIC-ACID
F. Gaymard et al., CHARACTERIZATION OF A FERRITIN MESSENGER-RNA FROM ARABIDOPSIS-THALIANA ACCUMULATED IN RESPONSE TO IRON THROUGH AN OXIDATIVE PATHWAY INDEPENDENT OF ABSCISIC-ACID, Biochemical journal, 318, 1996, pp. 67-73
A ferritin cDNA, AtFer1, from seedlings of Arabidopsis thaliana has be
en characterized. The deduced amino acid sequence of the AtFer1 protei
n indicates that A. thaliana ferritin shares the same characteristics
as the plant ferritin already characterized from the Leguminosae and G
raminacea families: (i) it contains an additional sequence in its N-te
rminal part composed of two domains: a transit peptide responsible for
plastid targeting and an extension peptide; (ii) amino acids that for
m the ferroxidase centre of H-type animal ferritin, as well as Glu res
idues characteristic of L-type animal ferritin, are conserved in AtFer
1; (iii) the C-terminal part of the A. thaliana ferritin subunit defin
ing the E-helix is divergent from its animal counterpart, and confirms
that 4-fold-symmetry axis channels are hydrophilic in plant ferritin.
Southern blot experiments indicate that AtFer1 is likely to be encode
d by a unique gene in the A. thaliana genome, although a search in the
NCBI dbEST database indicates that other ferritin genes, divergent fr
om AtFer1, may exist. Iron loading of A. thaliana plantlets increased
ferritin mRNA and protein abundance. In contrast to maize, the transcr
ipt abundance of a gene responding to abscisic acid (RAB18) did not in
crease in response to iron loading treatment, and A. thaliana ferritin
mRNA abundance is not accumulated in response to a treatment with exo
genous abscisic acid, at least in the culture system used in this stud
y. In addition, iron-induced increases in ferritin mRNA abundance were
the same as wild-type plants in abi1 and abi2 mutants of A. thaliana,
both affected in the abscisic acid response in vegetative tissues. In
creased AtFer1 transcript abundance in response to iron is inhibited b
y the antioxidant N-acetylcysteine. These results indicate that an oxi
dative pathway, independent of abscisic acid, could be responsible for
the iron induction of ferritin synthesis in A. thaliana.