Inhibition of nitric oxide production under alkaline condition regulates
iron homeostasis
Abstract
Rice is one of the most susceptible plant to iron (Fe) deficiency under
neutral and alkaline conditions. Alkaline stress induces H2O2 production
and increases the deposition of Fe on roots surface, which causes leaf
chlorosis and Fe deficiency in rice. Gene chip and qRT-PCR analysis
indicated that the expression of nitrate reductase (NR) genes were
down-regulated by alkaline treatment, which resulted in significantly
decreased nitrate activities and nitric oxide (NO) production in
epidermis and stele, where the H2O2 was accumulated. In contrast,
treatment with sodium nitroprusside (SNP), a NO donor, strongly
alleviates alkaline-induced Fe deficiency by limiting Fe plaque
formation. Increasing the NO signal significantly reduces the
accumulation of H2O2 and lignin barrier, but enhances phenolic acid
secretion in root epidermis and stele under alkaline stress. The
secreted phenolic acid effectively mobilized the apoplast Fe and
increased Fe uptake in root, thus which alleviate the Fe deficiency
response and down-regulate expression of Fe uptake genes under alkaline
condition. In conclusion, alkaline stress inhibits the NR activity and
NO production in roots of rice, which plays a vital role in mobilizing
the apoplast Fe by regulation of H2O2 and phenolic acids concentrations.