Genome-wide identification of the NAC transcription factors family and regulation of metabolites under salt stress in Isatis indigotica.

NAC (NAM, ATAF1/2 and CUC2) transcription factors (TFs) are a class of TFs families unique to plants, which not only play an important role in the growth and developmental stages of plants but also function in response to stress and regulation of secondary metabolite biosynthesis. However, there are few studies on NAC genes in the medicinal plant Isatis indigotica. In this study, 96 IiNAC genes were identified based on the whole-genome data of I. indigotica, distributed in seven chromosomes and three contigs. IiNAC genes were structurally conserved and divided into 15 subgroups. Cis-elements were identified in the promoter region of the IiNAC gene in response to plant growth and development, abiotic stresses and hormones. In addition, transcriptome and metabolome data of I. indigotica leaves under salt stress were analyzed to construct a network of IiNAC gene co-expression and metabolite association. Ten differentially expressed IiNAC genes were co-expressed with 109 TFs, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that most of these genes were associated with plant growth and development and abiotic stress responses. Eleven IiNAC genes were positively associated with 72 metabolites. Eleven IiNAC genes were positively or negatively associated with 47 metabolites through 37 TFs. Commonly associated secondary metabolites include two terpenoids, abscisic acid and bilobalide, two flavonoids, dihydrokaempferol and syringaldehyde, a coumarin, 7-methoxycoumarin, an alkaloid, lupinine, and quinone dihydrotanshinone I. This study provides important data to support the identification of the NAC gene family in I. indigotica and the regulatory functions of IiNAC genes in metabolites under salt stress.

[Identification of Carthamus tinctorius NAC gene family and analysis of drought stress response].

The NAC(NAM/ATAF/CUC) transcription factors are members of the largest transcriptional gene family in plants and play an essential role in the response of plants to drought stress. To identify the number and function of the NAC gene family in Carthamus tinctorius, the present study adopted bioinformatics methods to identify NAC gene family members based on the whole genome data of C. tinctorius, and analyzed their physicochemical properties, chromosomal location, phylogenetic relationship, gene structure, conserved domain, and conserved motif. Meanwhile, the real-time fluorescence-based quantitative RT-PCR(qRT-PCR) was used to analyze the transcription level of four NAC genes under drought stress in different time. The results showed that C. tinctorius contained 87 NAC genes unevenly distributed on 11 chromosomes, while no NAC gene was found on chromosome 12. The encoded proteins were 103-974 amino acids and the number of CDS ranged from 3 to 9. According to the phylogenetic relationships, 87 NAC genes were clustered into17 subfamilies. The analysis of conserved domains and motifs revealed that most of the genes contained five conserved subdomains, A-E and motif2 was the most conserved among NAC genes. The expression pattern analysis showed that the transcription levels of four NAC genes related to drought resistance were all up-regulated after drought stress treatment for different time, suggesting that these four NAC genes may be related to drought resistance of C. tinctorius. This study is expected to provide a theoretical basis for further functional analysis of NAC transcription factors in C. tinctorius and references for the cultivation of drought-tolerant C. tinctorius varieties.