Soybean metallothionein potential for bioremediation processes

BUSI, M.V.; CARRILLO, J.; PAGANI, M.A.; GOMEZ, M.S

San Martin

Congreso; The Fifth International Symposium on Enviromental Biotechnology and Engineering; 2016

UNSAM - 3IA Instituto de Investigación e Ingeniería Ambiental

Metallothioneins (MTs) are a ubiquitous family of cysteine rich proteins, deeplyresponsive to a wide range of stress factors and among them, specially heavymetals. Their main functions are related to heavy metal storage and detoxification.Animal and fungi MTs are highly characterized, by contrast, data on plantmetallothioneins are limited, even though many MT isoforms are present in theirgenomes. Considering plant metallothionein potential for bioremediation processes,two soybean MT isoforms were selected for further studies: GmMT1 and GmMT3,the most highly expressed isoforms in roots and shoots, respectively. Soybean, theworldwide main source of oil and high protein feeds for the livestock sector, has ahigh Cd accumulation capacity, and in all three cadmium levels tested theconcentration of the metal accumulated in the vegetal tissues analyzed was higherthan the available cadmium in the corresponding soil.Soybean MTs, purified from E.coli cells cultured in different metal rich media, areable to bind Cu, Cd and Zn with high stoichiometries. When these MTs areheterologously expressed in S. cerevisiae both proteins restore Cu tolerance andmarginally improve Zn tolerance of MT-null yeast strains, but GmMT3 is better forcoping with Cd stress. Moreover, A. thaliana plants expressing soybean MTs underthe CaMV35S promoter are able to grow better than wt plants in media with high Cu,Cd, and Zn concentrations.Altogether, our results confirm the promising potential of these plantmetallothioneins as heavy metal chelating agents. Different biotechnologicalapproaches may be implemented to take advantage of their useful properties inbioremediation strategies.