[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.

Transcriptome and miRNA sequencing analyses reveal the regulatory mechanism of α-linolenic acid biosynthesis in Paeonia rockii.

Paeonia rockii is a promising woody oil crop because its seeds are rich in polyunsaturated fatty acids especially α-linolenic acid (ALA). ALA is an essential fatty acid that the human body cannot synthesize and is the direct synthetic precursor of eicosapentaenoic and docosahexaenoic acids, which play crucial roles in the development of the blood vessels, brain and nervous system of humans. However, the mechanisms underlying the dynamic changes in ALA during seed development are unknown. In this study, we found that the fatty acid content gradually increased with P. rockii seed development, with ALA being the main unsaturated acid component (37-44%). The content of ALA reached the peak value of 306.26 mg/g DW 20 days before the seeds had fully maturated. Seeds from three different developmental stages were selected for transcriptome and miRNA sequencing analyses to explore the molecular mechanism of ALA accumulation in P. rockii seeds. A total of 39 differentially expressed genes were screened for their involvement in ALA biosynthesis, among which FAD2/8, GPAT, PDAT, LACS, LPAAT, and KAS II might be the key structural genes of ALA accumulation. The differential expression of these genes was dependent on the regulation of five miRNAs (mdm_miR156b, novel miR_91, novel miR_133, novel miR_291, and novel miR_405) and four transcription factors (AP2, SNL2, TGA-like, and SPL). This study reveals the mechanism behind the dynamic changes of ALA contents in P. rockii during seed development, and also provides an important theoretical basis for the breeding of excellent varieties of P. rockii.