Genome-Wide Identification and Expression Analysis of Gene Family Under Various Nitrogen Conditions in Avocado ( Mill.).

Avocado is an important economic fruit tree that requires a lot of nitrogen (N) to support growth and development. Nitrate transporter (NRT) gene family plays an essential role in N uptake and use in plants. However, no systematic identification of the NRT gene family has been reported in avocado. Bioinformatic analysis was used to identify and characterize the NRT gene family in avocado. The five N additions (29.75, 59.50, 119.00, 178.50, and 238.00 mg/L N) were used to identify the N requirement of avocado seedlings based on physiological indexes, while RNA-seq was conducted to analyze the response of under low-N and high-N conditions. Sixty-one members of the NRT gene family were identified and dispersed on 12 chromosomes in avocado. Many cis-regulatory elements (CREs) related to phytohormonal and stress response were found in the promoter regions. The avocado leaves in N3 have the highest activities of N-assimilating enzymes and N content as well as the lowest activities of antioxidant enzymes. Thus, 29.75 mg/L and 119.00 mg/L were chosen as low-N supply and normal-N supply for transcriptome analysis. The transcriptome analysis showed that , , , , , and and among members were up-regulated under normal-N condition in the leaves or roots, suggesting that these genes might affect N absorption under nitrate-sufficient conditions in avocado. RT-qPCR analysis found the relative expression patterns of selected genes among four samples were consistent with transcriptome data, suggesting that transcriptome data were reliable. This study would provide valuable information for identifying the functions of the gene family in avocado.