Absorption of cadmium accompanied by EDTA varies according to tomato cultivar

2019 
Two tomato (Lycopersicum solanum) varieties, one high (YSL189) and one low (HZ903) cadmium (Cd) accumulator, were used in our experiment. We detected cadmium (Cd ion/Cd-EDTA) uptake rates in roots and the corresponding expression of the Cd transport genes IRT1, IRT2, ZIP, Nramp1, Nramp2 and Nramp3. Our data proved that both cultivars – YSL189 and HZ903 – showed higher Cd accumulation in plants and a higher Cd uptake rate in roots supplied with Cd ion than with Cd-EDTA. In roots of YSL189, the expression levels of IRT1, IRT2, ZIP, Nramp1, Nramp3 and Nramp2 (5, 10 and 20 µmolc L–1 Cd) treated with Cd ion were higher than those treated with Cd-EDTA, whereas in roots of HZ903, only two genes, IRT1 and Nramp1 (5, 10, 100 µmolc L–1 Cd), showed higher expression levels in plants treated with Cd ion than in those treated with Cd-EDTA. When the difference between the cultivars was considered, the Cd concentration in the plant and the Cd uptake rate in the roots of YSL189 were higher than those of YZ903 under the same Cd treatments (i.e. Cd ion or Cd-EDTA). The expression of IRT2 and ZIP in the roots of YSL189 was higher than that observed in HZ903 treated with all levels of ion-Cd. We attribute the higher Cd uptake rate and greater accumulation of ion-Cd compared with EDTA-Cd in YSL189 than those found in HZ903 partly to the genes that had higher expression levels. Our results indicate that the roles of transporters in the absorption of different forms of Cd vary according to plant genotype.
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