Genome-Wide Identification and Expression Analysis of Nitrate Transporter (NRT) Gene Family in Eucalyptus grandis

Abstract

Eucalyptus grandis is an important planted hardwood tree worldwide with fast growth and good wood performance. The nitrate transporter (NRT) gene family is a major core involved in nitrogen (N) absorption and utilization in plants, but the comprehensive characterization of NRT genes in E. grandis remains mostly elusive. In this study, a total of 75 EgNRT genes were identified from the genome of E. grandis that were distributed unevenly across ten chromosomes, except Chr9. A phylogenetic analysis showed that the EgNRT proteins could be divided into three classes, namely NRT1, NRT2 and NRT3, which contained 69, 4 and 2 members, respectively. The cis-regulatory elements in the promoter regions of EgNRT genes were mainly involved in phytohormone and stress response. The transcriptome analysis indicated that the differentially expressed genes of leaf and root in E. grandis under different N supply conditions were mainly involved in the metabolic process and plant hormone signal transduction. In addition, the transcriptome-based and RT-qPCR analysis revealed that the expression of 13 EgNRT genes, especially EgNRT1.3, EgNRT1.38, EgNRT1.39 and EgNRT1.52, was significantly upregulated in the root under low-N-supply treatment, suggesting that those genes might play a critical role in root response to nitrate deficiency. Taken together, these results would provide valuable information for characterizing the roles of EgNRTs and facilitate the clarification of the molecular mechanism underlying EgNRT-mediated N absorption and distribution in E. grandis.