Maize plants have different strategies to protect their developing seeds against cadmium toxicity

Abstract

This work aimed to quantify the concentration of soluble amino acids, nitrogen (N) and Cd in the developing seeds of maize plants that were grown in Cd-contaminated soil from seed sowing to the reproductive stages. The specific activities and feedback inhibition properties of lysine (Lys) metabolic enzymes were also determined in developing seeds. The potential maize yield was depressed by Cd exposure. Cadmium concentration in plant organs followed the decreasing order: roots > stems = leaves > developing seeds (37.04, 1.95, 1.46 and 0.22 mg kg−1 Cd, respectively). The relatively low Cd concentration in the remained developing seeds was a result from root- and ear-mediated reductions of the Cd translocation in plants. Plants under Cd exposure presented developing seeds with an increased N concentration (up to 7%) when compared to control plants. Furthermore, the level of soluble amino acids (particularly histidine, glycine, tyrosine, methionine, isoleucine and valine) was increased in the developing seeds of Cd-treated plants. In addition, changes in the feedback properties of dihydrodipicolinate synthase (DHDPS), an enzyme from lysine metabolism, were observed in developing seeds. In conclusion, the current study showed that maternal plant exposure to Cd can alter the concentration of soluble amino acids and the behavior of Lys metabolic enzymes in developing seeds. This study provided not only new information about the influence of the long-term Cd exposure on plants, but also data about protective plant strategies against Cd toxicity.