NAC (NAM, ATAF1-2, and CUC2) transcription factors (TFs) play a vital role in plant growth and development, as well as in plant response to biotic and abiotic stressors (Duan et al., 2019; Guerin et al., 2019). Chrysanthemum is a plant with strong stress resistance and adaptability; therefore, a systematic study of NAC TFs in chrysanthemum is of great significance for plant breeding. In this study, 153 putative NAC TFs were identified based on the Chrysanthemum nankingense genome. According to the NAC family in Arabidopsis and rice, a rootless phylogenetic tree was constructed, in which the 153 CnNAC TFs were divided into two groups and 19 subfamilies. Moreover, the expression levels of 12 CnNAC TFs belonging to the OsNAC7 subfamily were analyzed in C. nankingense under osmotic and salt stresses, and different tissues were tested during different growth periods. The results showed that these 12 OsNAC7 subfamily members were involved in the regulation of root and stem growth, as well as in the regulation of drought and salt stresses. Finally, we investigated the function of the CHR00069684 gene, and the results showed that CHR00069684 could confer improved salt and low temperature resistance, enhance ABA sensitivity, and lead to early flowering in tobacco. It was proved that members of the OsNAC7 subfamily have dual functions including the regulation of resistance and the mediation of plant growth and development. This study provides comprehensive information on analyzing the function of CnNAC TFs, and also reveals the important role of OsNAC7 subfamily genes in response to abiotic stress and the regulation of plant growth. These results provide new ideas for plant breeding to control stress resistance and growth simultaneously.

Background: CRISPR/Cas9 is a rapidly developing genome editing technology in various biological systems due to its efficiency, portability, simplicity and versatility. This editing technology has been successfully applied in in several important plants of Solanaceae such as tomato, tobacco, potato, petunia and groundcherry. Wolfberry ranked the sixth among solanaceous crops of outstanding importance in China following potato, tomato, eggplant, pepper and tobacco. To date, there has been no report on CRISPR/Cas9 technology to improve Lycium ruthenicum due to the unknown genome sequencing and the lack of efficient regeneration and genetic transformation systems. Results: In this study, we have established an efficientregeneration and genetic transformation system of Lycium ruthenicum. We have used this system to validate target sites for fw2.2, a major fruit weight quantitative trait locus first identified from tomato and accounted for 30% of the variation in fruit size. In our experiments, the editing efficiency was very high, with 95.45% of the transgenic lines containing mutations in the fw2.2 target site. We obtained transgenic wolfberry plants containing four homozygous mutations and nine biallelic mutations in the fw2.2 gene. Conclusions: These results suggest that CRISPR-based gene editing is effective for the improvement of black wolfberry traits, and we expect this approach to be routinely applied to this important economic fruit.