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Putrescine enhances Fe deficiency-induced accumulation of nitric oxide which ultimately leads to the reutilization of cell wall Fe under Fe-deficient conditions.
Plants challenged with abiotic stress show enhanced polyamines levels. Here, we show that the polyamine putrescine (Put) plays an important role to alleviate Fe deficiency. The
adc2-1
mutant, which is defective in
Put
biosynthesis, was hypersensitive to Fe deficiency compared with wild type (Col-1 of Arabidopsis [
Arabidopsis thaliana
]). Exogenous
Put
decreased the Fe bound to root cell wall, especially to hemicellulose, and increased root and shoot soluble Fe content, thus alleviating the Fe deficiency-induced chlorosis. Intriguingly, exogenous
Put
induced the accumulation of nitric oxide (NO) under both Fe-sufficient (+Fe) and Fe-deficient (-Fe) conditions, although the ferric-chelate reductase (FCR) activity and the expression of genes related to Fe uptake were induced only under
-Fe
treatment. The alleviation of Fe deficiency by
Put
was diminished in the hemicellulose-level decreased mutant-
xth31
and in the
noa1
and
nia1nia2
mutants, in which the endogenous
NO
levels are reduced, indicating that both
NO
and hemicellulose are involved in Put-mediated alleviation of Fe deficiency. However, the
FCR
activity and the expression of genes related to Fe uptake were still up-regulated under -Fe+
Put
treatment compared with
-Fe
treatment in
xth31
, and Put-induced cell wall Fe remobilization was abolished in
noa1
and
nia1nia2
, indicating that Put-regulated cell wall Fe reutilization is dependent on NO. From our results, we conclude that
Put
is involved in the remobilization of Fe from root cell wall hemicellulose in a process dependent on
NO
accumulation under Fe-deficient condition in Arabidopsis.