A single recessive gene controls cadmium translocation in the cadmium hyperaccumulating rice cultivar Cho-Ko-Koku

Abstract

The heavy metal cadmium (Cd) is highly toxic to humans and can enter food chains from contaminated crop fields. Understanding the molecular mechanisms of Cd accumulation in crop species will aid production of safe Cd-free food. Here, we identified a single recessive gene that allowed higher Cd translocation in rice, and also determined the chromosomal location of the gene. The Cd hyperaccumulator rice variety Cho-Ko-Koku showed 3.5-fold greater Cd translocation than the no-accumulating variety Akita 63 under hydroponics. Analysis of an F(2) population derived from these cultivars gave a 1:3 segregation ratio for high:low Cd translocation. This indicates that a single recessive gene controls the high Cd translocation phenotype. A QTL analysis identified a single QTL, qCdT7, located on chromosome 7. On a Cd-contaminated field, Cd accumulation in the F(2) population showed continuous variation with considerable transgression. Three QTLs for Cd accumulation were identified and the peak of the most effective QTL mapped to the same region as qCdT7. Our data indicate that Cd translocation mediated by the gene on qCdT7 plays an important role in Cd accumulation on contaminated soil.

Detection of a QTL for accumulating Cd in rice that enables efficient Cd phytoextraction from soil

“…Physiological studies indicate that Choko-koku, Anjana Dhan, and Jarjan are characterized by a common Cd-transport process that enables an extremely high amount of Cd translocation from roots to shoots (Tezuka et al 2010, Ueno et al 2009, Uraguchi et al 2009). QTL analyses, including ours, identified major QTLs responsible for the high-Cd trait of these three cultivars in almost identical regions on chromosome 7 (Tezuka et al 2010, Ueno et al 2009).…”

“…Physiological studies indicate that Choko-koku, Anjana Dhan, and Jarjan are characterized by a common Cd-transport process that enables an extremely high amount of Cd translocation from roots to shoots (Tezuka et al 2010, Ueno et al 2009, Uraguchi et al 2009). QTL analyses, including ours, identified major QTLs responsible for the high-Cd trait of these three cultivars in almost identical regions on chromosome 7 (Tezuka et al 2010, Ueno et al 2009). Very recently, it has been revealed that OsHMA3, a P 1B -type ATPase, is encoded by a gene within the QTL region on chromosome 7 and plays an important role in controlling shoot Cd accumulation in rice (Miyadate et al 2011, Ueno et al 2010.…”

“…For field trials of phytoextraction, Murakami et al (2009) grew the Cd-accumulating rice cultivar Choko-koku for 2 years without irrigation after drainage; they reported that the soil Cd content and the grain Cd content in subsequently grown japonica rice were reduced by 38% and 47%, respectively. If the Jarjan allele at the qCdp7 locus is identical to the major QTL allele in Choko-koku (Tezuka et al 2010), the Jarjan allele of qCdp7 should also be useful for phytoextraction in Cd-polluted paddy fields. Although several of the BILs developed in this study might be suitable for phytoremediation of Cd, even more practical cultivars could be developed by using marker-assisted selection to introduce the Jarjan allele of qCdp7 into cultivars resistant to shattering and lodging and producing large biomass.…”

“…Several QTLs with major effects related to high ability to translocate Cd from roots to shoots at the seedling stage have also been found by using various rice mapping populations. For example, Tezuka et al (2010), who studied an F 2 population between Choko-koku (a high-Cd indica cultivar) and Akita 63 (a low-Cd japonica cultivar), found a single recessive QTL on chromosome 7. The variety Choko-koku has been selected as a candidate phytoremediator for paddy fields contaminated with low to moderate levels of Cd, and a field trial of phytoextraction by using this cultivar has been launched (Murakami et al 2009).…”

Role of the iron transporter OsNRAMP1 in cadmium uptake and accumulation in rice

“…[17][18][19] The gene responsible for the QTL effect has been identified as OsHMA3 in the Cho-kokoku and Anjana Dhan cultivars, 20,21 but the gene in Habataki has not yet been identified. The amino acid at position 80 in OsHMA3 is critical for its transport Proposed model for the role of OsNramP1 in cd translocation from the root to the shoot.…”