Reference "Three rice nicotianamine synthase genes, OsNAS1, OsNAS2, and OsNAS3 are expressed in cells involved in long-distance transport of iron and differentially regulated by iron"

Reference ID

25480

Title

Three rice nicotianamine synthase genes, OsNAS1, OsNAS2, and OsNAS3 are expressed in cells involved in long-distance transport of iron and differentially regulated by iron

Source

The Plant journal : for cell and molecular biology, 2003, vol. 36, pp. 366-381

Authors (6)

Inoue-H	Higuchi-K
Takahashi-M	Nakanishi-H
Mori-S	Nishizawa-N-K

Abstract

Nicotianamine (NA), a chelator of metals, is ubiquitously present in higher
plants. In graminaceous plants, NA is a biosynthetic precursor of
phytosiderophores and is thus a crucial component for iron (Fe) acquisition.
Here, we show that three rice NA synthase (NAS) genes, OsNAS1, OsNAS2, and
OsNAS3 are expressed in cells involved in long-distance transport of Fe and that
the three genes are differentially regulated by Fe. OsNAS1 and OsNAS2
transcripts were detected in Fe-sufficient roots but not in leaves, and levels
of both increased markedly in both roots and leaves in response to Fe
deficiency. In contrast, the OsNAS3 transcript was present in leaves but was
very low in roots of Fe-sufficient plants. Further, OsNAS3 expression was
induced in roots but was suppressed in leaves in response to Fe deficiency. Promoter-
GUS analysis revealed that OsNAS1 and OsNAS2 were expressed in Fe-sufficient
roots in companion cells and pericycle cells adjacent to the protoxylem. With Fe
deficiency, OsNAS1 and OsNAS2 expression extended to all root cells along with
an increase in phytosiderophore secretion. In Fe-deficient plants, OsNAS1 and
OsNAS2 were expressed in the vascular bundles of green leaves and in all cells
of leaves showing severe chlorosis. OsNAS3 expression was restricted to the
pericycle and companion cells of the roots, and in companion cells of leaves
irrespective of Fe status. These results strongly suggested that NAS and NA play
an important role in long-distance transport of Fe in rice plants, in addition
to their roles in phytosiderophore secretion from roots.