Abstract
Cadmium (Cd), one of the heavy metal pollution sources, has a strong
impact on crop growth and development, yield formation, and food safety.
In this work, we perform the first comprehensive study on the molecular
mechanisms of wheat (Triticum aestivum L.) selenium-binding
protein-A (TaSBP-A) that is involved in Cd-tolerance. As a cytoplasm
protein, TaSBP-A was highly conservative in plants, but showed a high
expression in plant roots; moreover, both transcription and translation
expression levels were highly induced by Cd stress. TaSBP-A
overexpression in yeast, Arabidopsis and wheat protoplasts enhanced
Cd-tolerance via free Cd2+ accumulation and
detoxification. In vitro Cd2+ binding assay combined
with a thermodynamics survey by isothermal titration calorimetry as well
as secondary structure analysis by circular dichroism showed that the
CXXC motif in TaSBP-A was a major Cd-binding site that played important
roles in the detoxification under Cd stress via its interaction with
free Cd2+. Our results provide new insights into the
molecular mechanism of plant Cd-tolerance as well as into the candidate
gene for improving crop heavy metal resistance.