Characterization and the Expression Analysis of Nitrate Transporter (NRT) Gene Family in Pineapple

Nitrate is the preferred nitrogen source of higher plants and an essential nutrient for plant growth and development. Nitrate transporters (NRTs) play vital roles in the nitrate uptake and transportation. However, the NRT gene family in pineapple is still unexplored. In this study, we performed a genome-wide analysis of the pineapple genome and identified 48 NRT genes (AcNRTs) distributed unevenly across 9 chromosomes and 2 scaffolds. Phylogenetic analysis showed that these genes can be divided into three groups, namely, AcNRT1/PTR, AcNRT2 and AcNRT3/NAR1 with 44, 3 and 1 members, respectively. AcNRTs within the same phylogenetic group share similar gene structure and domain composition. In addition, syntenic and phylogenetic analyses identified 34 Arabidopsis NRT genes with 31 pineapple NRT genes as orthologs. By investigating the expression profiles of these genes in various tissues, we showed that the expression pattern of some AcNRTs genes is tissue-specific. Furthermore, we examined the expression of the AcNRT2s under nitrate starvation and found that AcNRT2.1 and AcNRT2.2 both have the strongest response in roots suggesting that AcNRTs may play a broad role in the pineapple in response to nitrate deficiency. Taken together, our data provide insights into the evolution and function of pineapple NRTs and pave a path for future functional investigation of pineapple NRTs genes.