The difference of cadmium accumulation between the indica and japonica subspecies and the mechanism of it
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Many studies have shown genotypic differences in Cadmium (Cd) accumulation among rice cultivars, and concentrations in shoots and grains are generally higher in indica rice cultivars than in japonica rice cultivars, but the mechanism remains unknown. The main objective of this study was to investigate differences in heavy metal accumulation between rice subspecies through the analysis of 46 indica cultivars and 30 japonica cultivars. At the seedling stage, the mean Cd concentrations in the shoots of indica subspecies were significantly higher than those in japonica subspecies (1.22-fold), but this pattern was not observed in the roots. At the filling stage, the mean Cd concentrations in the shoots and spikes of indica subspecies were 1.66- and 2.14-fold higher than the respective concentrations in japonica subspecies. At the harvest stage, the mean Cd concentrations in the shoots and brown rice of indica subspecies were 1.61- and 2.27-fold higher than the respective concentrations in japonica subspecies. These results indicate that root-to-shoot and shoot-to-grain translocation, rather than Cd absorption in the roots, may be the key processes that determine the differences in Cd accumulation among rice subspecies. Gene expression analysis revealed that overall, the expression levels of the Cd transporter gene OsNramp1 notably increased (22.46-fold), but the expression levels of OsHMA2, OsHMA3 and OsNRAMP5 were not significantly changed at the seedling stage in the 76 cultivars exposed to Cd; the expression levels of OsNramp1 were positively correlated with the Cd concentrations in spikes at the filling stage. In addition, a significant difference was observed in the expression levels of OsNramp1 between the indica and japonica subspecies, which may explain the higher Cd concentrations in roots but lower Cd concentrations in spikes and brown rice for the japonica subspecies. Together, these results demonstrate that OsNramp1 may be the most important gene among the four selected genes in the promotion of Cd uptake by roots and transfer of Cd into spikes and eventually into brown rice.
KeywordsCadmium accumulation Rice subspecies Translocation Cd transporter Gene expression
Translocation factor of root to shoot
This work was supported by a Special Fund for Agro-Scientific Research in the Public Interest (No. 201403015), the National Natural Science Foundation of China (No. 31571616) and Funds for Science and Technology Innovation Project from the Chinese Academy of Agricultural Sciences. We gratefully acknowledge Dr. Da-Li Zeng, China National Rice Research Institute, China, for supplying seeds of the 76 selected cultivars.
- Cheng KS (1988) A statistical evaluation of the classification of rice cultivars into hsien and keng subspecies. Rice Genet Newslett 4:46–48Google Scholar
- Fujimaki S, Suzui N, Ishioka NS, Kawachi N, Ito S, Chino M, Nakamura S (2010) Tracing cadmium from culture to spikelet: noninvasive imaging and quantitative characterization of absorption, transport, and accumulation of cadmium in an intact rice plant. Plant Physiol 152:1796–1806. doi: 10.1104/pp.109.151035 CrossRefPubMedPubMedCentralGoogle Scholar
- Ishikawa S, Ishimaru Y, Igura M, Kuramata M, Abe T, Senoura T, Hase Y, Arao T, Nishizawa NK, Nakanishi H (2012) Ion-beam irradiation, gene identification, and marker-assisted breeding in the development of low-cadmium rice. Proc Natl Acad Sci USA 109:19166–19171. doi: 10.1073/pnas.1211132109 CrossRefPubMedPubMedCentralGoogle Scholar
- Kuramata M, Masuya S, Takahashi Y, Kitagawa E, Inoue C, Ishikawa S, Youssefian S, Kusano T (2009) Novel cysteine-rich peptides from Digitaria ciliaris and Oryza sativa enhance tolerance to cadmium by limiting its cellular accumulation. Plant Cell Physiol 50:106–117. doi: 10.1093/pcp/pcn175 CrossRefPubMedGoogle Scholar
- Satoh-Nagasawa N, Mori M, Nakazawa N, Kawamoto T, Nagato Y, Sakurai K, Takahashi H, Watanabe A, Akagi H (2012) Mutations in rice (Oryza sativa) heavy metal ATPase 2 (OsHMA2) restrict the translocation of zinc and cadmium. Plant Cell Physiol 53:213–224. doi: 10.1093/pcp/pcr166 CrossRefPubMedGoogle Scholar
- Uraguchi S, Kamiya T, Sakamoto T, Kasai K, Sato Y, Nagamura Y, Yoshida A, Kyozuka J, Ishikawa S, Fujiwara T (2011) Low-affinity cation transporter (OsLCT1) regulates cadmium transport into rice grains. Proc Natl Acad Sci USA 108:20959–20964. doi: 10.1073/pnas.1116531109 CrossRefPubMedPubMedCentralGoogle Scholar
- Zhou H, Zeng M, Zhou X, Liao BH, Liu J, Lei M, Zhong QY, Zeng H (2013) Assessment of heavy metal contamination and bioaccumulation in soybean plants from mining and smelting areas of southern Hunan Province, China. Environ Toxicol Chem 32:2719–2727. doi: 10.1002/etc.2389 CrossRefPubMedGoogle Scholar