The knockdown of OsVIT2 and MIT affects iron localization in rice seed
© Bashir et al.; licensee Springer. 2013
Received: 14 May 2013
Accepted: 12 September 2013
Published: 20 November 2013
The mechanism of iron (Fe) uptake in plants has been extensively characterized, but little is known about how Fe transport to different subcellular compartments affects Fe localization in rice seed. Here, we discuss the characterization of a rice vacuolar Fe transporter 2 (OsVIT2) T-DNA insertion line (osvit2) and report that the knockdown of OsVIT2 and mitochondrial Fe transporter (MIT) expression affects seed Fe localization.
osvit2 plants accumulated less Fe in their shoots when grown under normal or excess Fe conditions, while the accumulation of Fe was comparable to that in wild-type (WT) plants under Fe-deficient conditions. The accumulation of zinc, copper, and manganese also changed significantly in the shoots of osvit2 plants. The growth of osvit2 plants was also slow compared to that of WT plants. The concentration of Fe increased in osvit2 polished seeds. Previously, we reported that the expression of OsVIT2 was higher in MIT knockdown (mit-2) plants, and in this study, the accumulation of Fe in mit-2 seeds decreased significantly.
These results suggest that vacuolar Fe trafficking is important for plant Fe homeostasis and distribution, especially in plants grown in the presence of excess Fe. Moreover, changes in the expression of OsVIT2 and MIT affect the concentration and localization of metals in brown rice as well as in polished rice seeds.
KeywordsIron Manganese Mitochondrial iron transporter Oryza sativa Vacuolar iron transporter Zinc
Iron (Fe) is an essential micronutrient for all higher organisms. Plants require Fe for several cellular processes, including respiration, chlorophyll biosynthesis, and photosynthetic electron transport (Marschner 1995). The molecular mechanism of Fe transport in rice has been well documented (Bashir et al. 2006; Bashir and Nishizawa 2006; Bashir et al. 2010; Bashir et al. 2011b; Bashir et al. 2013a; Ishimaru et al. 2012; Kobayashi and Nishizawa 2012). Once inside a plant, Fe enters root cells and is transported to the shoot and seeds. Fe performs vital roles in subcellular organelles such as chloroplasts and mitochondria, and defects in mitochondrial Fe homeostasis significantly affect plant growth (Bashir et al. 2011a; Bashir et al. 2011c; Ishimaru et al. 2009). As excess Fe in the cytoplasm may be toxic, it is either stored as ferritin in chloroplasts or is diverted to the vacuole. Knockout mutants for the rice vacuolar metal transporters OsVIT1 and OsVIT2 were recently reported to accumulate increased amounts of Fe in their seeds (Zhang et al. 2012). This accumulation was mainly observed in the embryo (Zhang et al. 2012), which is removed during milling. In this short report, we describe the characterization of a mutant in which the expression of OsVIT2 was knocked down and we show that changes in the expression of OsVIT2 and mitochondrial iron transporter (MIT) affect seed Fe localization in brown rice as well as in polished rice seeds.
This study was supported by a grant from the Ministry of Agriculture, Forestry and Fisheries of Japan (Green Technology Project IP-5003).
In our previous report (Bashir et al. 2011c), OsVIT2 was referred to as OsVIT1, while Zhang et al. (2012) used the name OsVIT2 for the same gene. To avoid confusion, in this study we changed the name of OsVIT1 to OsVIT2.
- An S, Park S, Jeong D-H, Lee D-Y, Kang H-G, Yu J-H, Hur J, Kim S-R, Kim Y-H, Lee M, Han S, Kim S-J, Yang J, Kim E, Wi SJ, Chung HS, Hong J-P, Choe V, Lee H-K, Choi J-H, Nam J, Kim S-R, Park P-B, Park KY, Kim WT, Choe S, Lee C-B, An G: Generation and analysis of end aequence satabase for T-DNA tagging lines in rice. Plant Physiol 2003a,133(4):2040–2047. doi:10.1104/pp. 103.030478 doi:10.1104/pp.103.030478View ArticleGoogle Scholar
- Bashir K, Nishizawa NK: Deoxymugineic acid synthase: a gene important for fe-acquisition and homeostasis. Plant Signal Behav 2006,1(6):290–292. 10.4161/psb.1.6.3590PubMed CentralView ArticlePubMedGoogle Scholar
- Bashir K, Inoue H, Nagasaka S, Takahashi M, Nakanishi H, Mori S, Nishizawa NK: Cloning and characterization of deoxymugineic acid synthase genes from graminaceous plants. J Biol Chem 2006,281(43):32395–32402. doi:10.1074/jbc.M604133200View ArticlePubMedGoogle Scholar
- Bashir K, Ishimaru Y, Nishizawa NK: Iron uptake and loading into rice grains. Rice 2010,3(2):122–130. doi:10.1007/s12284–010–9042-yView ArticleGoogle Scholar
- Bashir K, Ishimaru Y, Nishizawa NK: Identification and characterization of the major mitochondrial Fe transporter in rice. Plant Signal Behav 2011,6(10):1591–1593. 10.4161/psb.6.10.17132PubMed CentralView ArticlePubMedGoogle Scholar
- Bashir K, Ishimaru Y, Shimo H, Kakei Y, Senoura T, Takahashi R, Sato Y, Sato Y, Uozumi N, Nakanishi H, Nishizawa NK: Rice phenolics efflux transporter 2 (PEZ2) plays an important role in solubilizing apoplasmic iron. Soil Sci Plant Nutr 2011,57(6):803–812. doi:10.1080/00380768.2011.637305View ArticleGoogle Scholar
- Bashir K, Ishimaru Y, Shimo H, Nagasaka S, Fujimoto M, Takanashi H, Tsutsumi N, An G, Nakanishi H, Nishizawa NK: The rice mitochondrial iron transporter is essential for plant growth. Nat Commun 2011, 2: 322. doi:10.1038/ncomms1326PubMed CentralView ArticlePubMedGoogle Scholar
- Bashir K, Ishimaru Y, Nishizawa NK: Molecular mechanisms of zinc uptake and translocation in rice. Plant Soil 2012, 361: 189–201. doi:10.1007/s11104-012-1240-5View ArticleGoogle Scholar
- Bashir K, Nozoye T, Ishimaru Y, Nakanishi H, Nishizawa NK: Exploiting new tools for iron bio-fortification of rice: biotechnology advances. 2013a,31(8):1624–1633.http://dx.doi.org/10.1016/j.biotechadv.2013.08.012 doi:Google Scholar
- Bashir K, Takahashi R, Nakanishi H, Nishizawa NK: The road to micronutrient biofortification of rice: progress and prospects. Front Plant Sci 2013., 4(15): doi:10.3389/fpls.2013.00015Google Scholar
- Ishimaru Y, Bashir K, Fujimoto M, An G, Itai RN, Tsutsumi N, Nakanishi H, Nishizawa NK: Rice-specific mitochondrial iron-regulated gene (MIR) plays an important role in iron homeostasis. Mol Plant 2009,2(5):1059–1066. doi:10.1093/mp/ssp051View ArticlePubMedGoogle Scholar
- Ishimaru Y, Takahashi R, Bashir K, Shimo H, Senoura T, Sugimoto K, Ono K, Yano M, Ishikawa S, Arao T, Nakanishi H, Nishizawa NK: Characterizing the role of rice NRAMP5 in manganese, iron and cadmium transport. Sci Rep 2012., 2: doi:10.1038/srep00286Google Scholar
- Jeong D-H, An S, Park S, Kang H-G, Park G-G, Kim S-R, Sim J, Kim Y-O, Kim M-K, Kim S-R, Kim J, Shin M, Jung M, An G: Generation of a flanking sequence-tag database for activation-tagging lines in japonica rice. Plant J 2006,45(1):123–132. doi:10.1111/j.1365–313X.2005.02610.xView ArticlePubMedGoogle Scholar
- Kim SA, Punshon T, Lanzirotti A, Li L, Alonso JM, Ecker JR, Kaplan J, Guerinot ML: Localization of iron in Arabidopsis seed requires the vacuolar membrane transporter VIT1. Science 2006,314(5803):1295–1298. doi:10.1126/science.1132563View ArticlePubMedGoogle Scholar
- Kobayashi T, Nishizawa NK: Iron uptake, translocation, and regulation in higher plants. Annu Rev Plant Biol 2012,63(1):131–152. doi:10.1146/annurev-arplant-042811–105522View ArticlePubMedGoogle Scholar
- Marschner H: Mineral nutrition of higher plants. 2nd edition. London: Academic Press; 1995.Google Scholar
- Sato Y, Antonio B, Namiki N, Motoyama R, Sugimoto K, Takehisa H, Minami H, Kamatsuki K, Kusaba M, Hirochika H, Nagamura Y: Field transcriptome revealed critical developmental and physiological transitions involved in the expression of growth potential in japonica rice. BMC Plant Biol 2011,11(1):10. 10.1186/1471-2229-11-10PubMed CentralView ArticlePubMedGoogle Scholar
- Sato Y, Antonio BA, Namiki N, Takehisa H, Minami H, Kamatsuki K, Sugimoto K, Shimizu Y, Hirochika H, Nagamura Y: RiceXPro: a platform for monitoring gene expression in japonica rice grown under natural field conditions. Nucleic Acids Res 2011,39(suppl 1):D1141-D1148. doi:10.1093/nar/gkq1085PubMed CentralView ArticlePubMedGoogle Scholar
- Vigani G, Zocchi G, Bashir K, Philippar K, Briat J-F: Signals from chloroplasts and mitochondria for iron homeostasis regulation. Trends Plant Sci 2013,18(6):305–311. doi: http://dx.doi.org/10.1016/j.tplants.2013.01.006 doi: 10.1016/j.tplants.2013.01.006View ArticlePubMedGoogle Scholar
- World Health Organization: Summary and conclusion of the sixty-first meeting of the joint FAO/WHO expert committee on food additives. World Health Organization; 2003. http://www.who.int/foodsafety/chem/jecfa/summaries/en/summary_61.pdfGoogle Scholar
- Zhang Y, Xu Y-H, Yi H-Y, Gong J-M: Vacuolar membrane transporters OsVIT1 and OsVIT2 modulate iron translocation between flag leaves and seeds in rice. Plant J 2012, 72: 400–410. doi:10.1111/j.1365–313X.2012.05088.xView ArticlePubMedGoogle Scholar
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