Reference "Iron induces ferritin synthesis in maize plantlets"

Reference ID

7185

Title

Iron induces ferritin synthesis in maize plantlets

Source

Plant molecular biology, 1992, vol. 19, pp. 563-575

Authors (3)

Lobreaux-S	Massenet-O
Briat-J-F

Abstract

The iron-storage protein ferritin has been purified to homogeneity from maize
seeds, allowing to determine the sequence of the first 29 NH2-terminal amino
acids of its subunit and to raise specific rabbit polyclonal antibodies.
Addition of 500 microM Fe-EDTA/75 microM Fe-citrate to hydroponic culture
solutions of maize plantlets, previously starved for iron, led to a significant
increase of the iron concentration of roots and leaves, albeit root iron was
mainly found associated with the apoplast. Immunodetection of ferritin by
western blots indicated that this iron treatment induced ferritin protein
accumulation in roots and leaves over a period of 3 days. In order to
investigate this induction at the ferritin mRNA level, various ferritin cDNA
clones were isolated from a cDNA library prepared from poly(A)+ mRNA isolated
from roots 48 h after iron treatment. These cDNAs were classified into two
groups called FM1 and FM2. Upstream of the sequence encoding the mature ferritin
subunit, both of these cDNAs contained an in-frame coding sequence with the
characteristics of a transit peptide for plastid targeting. Two members of the
FM1 subfamily, both partial at their 5' extremity, were characterized. They are
identical, except in their 3' untranslated region: FM1A extends 162 nucleotides
beyond the 3' terminus of FM1B. These two mRNAs could arise from the use of two
different polyadenylation signals. FM2 is 96% identical to FM1 and contains 45
nucleotides of 5' untranslated region. Northern analyses of root and leaf RNAs,
at different times after iron treatment, revealed ferritin mRNA accumulation in
response to iron. Ferritin mRNA accumulation was transient and particularly
abundant in leaves, reaching a maximum at 24 h. The level of ferritin mRNA in
roots was affected to a lesser extent than in leaves.