Genome-wide identification and expression analysis of the ZIP gene family in Quercus dentata

The ZIP (Zn-regulated, iron-regulated transporter-like protein) gene family is a novel metal transporter that is capable of absorbing and transporting a variety of metal cations, including zinc (Zn), iron (Fe), manganese (Mn), and cadmium (Cd). Quercus dentata Thunb. is a candidate plant species for the phytoremediation of heavy metal contaminated soil. A chromosome-scale genome assembly is reported recently for Q. dentata, however, genome-wide analysis of ZIP genes has not been performed. In this study, we identified 29 ZIP genes in Q. dentata genome using bioinformatics tools. The sequence homology, chromosomal distribution and phylogenetic relationship of these genes with ZIP genes from other plants indicated potential gene duplication during Q. dentata genome evolution. Sequence analysis revealed 23 conserved motifs in QdZIP proteins and 11 types of high-frequency cis-acting elements in the promoters of QdZIP genes. QdZIP proteins were predicted to localize on cell membrane except QdZIP7. QdZIP7 was predicted to be a chloroplast protein, which was confirmed using microscopic observation of QdZIP7-GFP fusion protein. QdZIP gene expression patterns in roots and exophytic mycorrhiza, leaves, stems and fruits were obtained from transcriptome data, and the responsiveness of QdZIP7 to excessive heavy metal Zn was detected using qRT-PCR. In summary, our study provided a basic sights on the ZIP gene family in Q. dentata, laying the foundation for in-depth investigation on the roles of the ZIP proteins in heavy metal transport.