Metallothioneins (MTs) are small proteins with a high content of cysteine residues that bind various heavy metals. Plant MTs are classified into four types based on the arrangement of cysteine residues, and all are involved in copper and other metals homeostasis [, ]. This entry represents MT3 that in Arabidopsis is predominantly expressed in leaf mesophyll cells. It functions as copper (Cu) and zinc (Zn) chelator and plays a role in Cu homeostasis, specifically in the remobilization of Cu from senescing leaves. The mobilization of Cu is important for seed development [, ].
