Genome-wide identification of the NRAMP gene family in kiwifruit and the response of AcNRAMP7 to cadmium stress

The NRAMP gene family acts on a wide range of divalent metal ions in plants and plays a key role in Cd accumulation and resistance in plants. In this study, we identified 12 AcNRAMP genes from the kiwifruit genome that were phylogenetically categorized into four groups. Chromosome distribution analysis revealed that 11 of the 12 AcNRAMP genes were unevenly distributed on seven chromosomes. The AcNRAMP gene promoter cis-elements were mainly categorized into hormone-associated cis-acting elements and environmental stress-associated cis-acting elements. In addition, expression profiling revealed that three genes were significantly differentially expressed in the roots and that two genes were markedly differentially expressed in the leaves. Based on the AcNRAMP family analysis by RT-PCR, we hypothesized that there might be a mechanism by which members of the AcNRAMP gene family respond to Cd stress: after being subjected to high concentrations of Cd stress, the expression of AcNRAMP7 and AcNRAMP10 was downregulated in roots, whereas the expression of AcNRAMP6 was upregulated in leaves, the concentration of Cd translocated to the root cells was reduced, and the environmental Cd in the environment decreased the degree of damage to plant root cells, which in turn led to an increase in Cd tolerance in kiwifruit plants and resulted in slower root growth. The results of this study are crucial, as they lay the foundation for further exploration of the regulatory functions of AcNRAMPs in kiwifruit in response to Cd stress.