Soybean metallothionein family: a role in cadmium accumulation?

PAGANI MA; CARRILLO J; REGGIARDO M; TOMAS M; ANDREO CS; CAPDEVILA M; BOFILL R; ATRIAN S

Barcelona

Simposio; 11th International Symposium on Applied Bioinorganic Chemistry; 2011

Universidad de Barcelona, Universidad Autónoma de Barcelona, España.

Cadmium (Cd) is a highly toxic heavy metal for both plants and animals. The presence of Cd in agricultural soils is of great concern regarding its entry into the food chain [1]. Compounds of Cd are soluble, so they are readily taken up by plants, and accumulated in edible parts. Soybean, for instance, shows high levels of Cd concentration in grains. In this context, the study of its molecular determinants of Cd accumulation -such as metallothioneins (MT)? is of great importance. Four MT genes/proteins, belonging to the 4 plant MTs types [2], are currently under studies. All of them are expressed at high levels in soybean tissues: MT1, 2 and 3 in root, shoot and seeds, and MT4 only in seeds. Heterologous expression in MT-null S. cerevisiae strains restores Cd tolerance but only marginally enhances Zn tolerance; also it improves resistance to different oxidative stress agents. Soybean MTs, obtained through recombinant synthesis in E. coli cells cultured in metal supplemented media, render better folded polypeptides with Cd than with Zn. These results point towards a role in metal sequestration, with preference of Cd over its physiological chemical equivalent ?zinc-, and/or palliation of the oxidative stress induced by heavy metals in excess, for all soybean MTs studied.