4.1. Identification of NAGs in Brassica napus

Firstly, the aa sequences of NAGs were retrieved and obtained from the Arabidopsis Information Resource (TAIR) database (https://www.Arabidopsis.org/, accessed on 28 August 2019), and then were used for a BLASTP search in the B. napus genome database (http://www.genoscope.cns.fr/brassicanapus/, accessed on 28 August 2019) [54]. Redundant sequences were removed manually. The Pfam database (http://pfam.xfam.org/, accessed on 28 August 2019) was used to identify standard genes with E-value ≤ 0.001. To confirm the accuracy of the genes, all candidate genes were aligned with Arabidopsis homologous genes. The genomic DNA, cDNA, CDS and protein sequences of the NAGs were obtained from the B. napus genome database [28]. The NAGs in B. rapa and B. oleracea were identified by the same methods shown above, and the corresponding sequences were obtained from the Brassica Database (BRAD, http://brassicadb.org/brad, accessed on 10 September 2019). The confirmed NAGs were renamed using the abbreviation of species name, the chromosome position, and the name of Arabidopsis homologous genes. e.g., BnaC03.ASN1.