Identification, characterization, and expression analysis of metal tolerance protein (MTP) genes in Alternanthera philoxeroides

Metal tolerant protein (MTP) is an important member of the cation transporter (cation diffusion facilitator, CDF) family and plays an important role in heavy metal transport and detoxification by plants. In the present study, MTP sequences from model plants and BLAST analysis were used to identify a total of 40 MTP genes in the genome of Alternanthera philoxeroides, and a variety of bioinformatics analysis software and online tools were used for the bioinformatics analysis (e.g., phylogenetic reconstruction, conserved domain analyses and gene structure analysis of the identified genes). The results showed that most of those 40 identified ApMTP genes contained two to six transmembrane domains (TMD), and phylogenetic analysis indicated that the genes belonged to the Fe/Zn-CDF (7), Mn-CDF (20), and Zn-CDF (13) sub-families. Furthermore, a conserved motif (HXXXD) was identified on or around the TMD-II and TMD-V of the Zn-CDF and Zn/Fe-CDF subfamily members, and another (DXXXD) was identified on the TMD-II and TMD-V of the Mn-CDFs subfamily members. The expression pattern of each gene was investigated by extracting relevant information from NCBI. The expression pattern analysis showed that ApMTP has the characteristics of tissue specific expression and response to different treatments such as root hypokalemia.