Bioinformatics analysis of the MTP gene family in Amaranthus hypochondriacus L. and expression characteristics under cadmium stress

Metal tolerance protein (MTP), also known as cation diffusion facilitator (CDF), is a metal ion transport-related protein. To study the sequence characteristics and evolutionary relationships of the MTP gene family in Amaranthus hypochondriacus L., and to predict the functions and regulatory mechanisms of its members, we took the latest A. hypochondriacus genome as a reference and identified a total of nine members of the A. hypochondriacus MTP family. According to their sequence characteristics, they were divided into three subgroups: Zn-CDF (3), Zn/Fe-CDF (4), and Mn-CDF (4). All family members contained a cation_efflux domain, a typical feature of MTP transporters, with some also containing a ZT_dimer domain. Chromosome mapping showed that the nine MTP genes were distributed on seven chromosomes. Under cadmium (Cd) stress, the expression levels of AhMTP7 and AhMTP9 were inhibited in both leaves and roots, while the expression level of AhMTP6 was inhibited in leaves but induced in roots. The expression levels of the other six AhMTPs were induced by Cd, with AhMTP2 and AhMTP3 only induced in leaves, and AhMTP5 only induced in roots. Promoter cis-acting element analysis identified several cis-acting elements in the AhMTP promoter for stress response, growth and development, and hormone signaling. MicroRNA (miRNA) prediction analysis showed that 15 miRNAs targeted seven AhMTPs.