Iron fortification of rice seeds through activation of the nicotianamine synthase gene.
The most widespread dietary problem in the world is mineral deficiency. We used the nicotianamine synthase (NAS) gene to increase mineral contents in rice grains. Nicotianamine (NA) is a chelator of metals and a key component of metal homeostasis. We isolated activation-tagged mutant lines in which expression of a rice NAS gene, OsNAS3, was increased by introducing 35S enhancer elements. Shoots and roots of the OsNAS3 activation-tagged plants (OsNAS3-D1) accumulated more Fe and Zn. Seeds from our OsNAS3-D1 plants grown on a paddy field contained elevated amounts of Fe (2.9-fold), Zn (2.2-fold), and Cu (1.7-fold). The NA level was increased 9.6-fold in OsNAS3-D1 seeds. Analysis by size exclusion chromatography coupled with inductively coupled plasma mass spectroscopy showed that WT and OsNAS3-D1 seeds contained equal amounts of Fe bound to IP6, whereas OsNAS3-D1 had 7-fold more Fe bound to a low molecular mass, which was likely NA. Furthermore, this activation led to increased tolerance to Fe and Zn deficiencies and to excess metal (Zn, Cu, and Ni) toxicities. In contrast, disruption of OsNAS3 caused an opposite phenotype. To test the bioavailability of Fe, we fed anemic mice with either engineered or WT seeds for 4 weeks and measured their concentrations of hemoglobin and hematocrit. Mice fed with engineered seeds recovered to normal levels of hemoglobin and hematocrit within 2 weeks, whereas those that ate WT seeds remained anemic. Our results suggest that an increase in bioavailable mineral content in rice grains can be achieved by enhancing NAS expression.
Lee
Sichul
S
Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea.
Jeon
Un Sil
US
Lee
Seung Jin
SJ
Kim
Yoon-Keun
YK
Persson
Daniel Pergament
DP
Husted
Søren
S
Schjørring
Jan K
JK
Kakei
Yusuke
Y
Masuda
Hiroshi
H
Nishizawa
Naoko K
NK
An
Gynheung
G
D000222:Adaptation, Physiological; D019883:Alkyl and Aryl Transferases / Q000235:genetics*; D018798:Anemia, Iron-Deficiency / Q000628:therapy; D000821:Animal Feed; D000818:Animals; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D007501:Iron / Q000008:administration & dosage*; D013058:Mass Spectrometry; D019216:Metals, Heavy / Q000633:toxicity; D051379:Mice; D009154:Mutation; D012275:Oryza / Q000196:embryology / Q000201:enzymology / Q000235:genetics* / Q000502:physiology; D012639:Seeds / Q000378:metabolism*
D019216:Metals, Heavy; D007501:Iron; D019883:Alkyl and Aryl Transferases; C118230:nicotianamine synthase