BcERF070, a novel ERF (ethylene-response factor) transcription factor from non-heading Chinese cabbage, affects the accumulation of ascorbic acid by regulating ascorbic acid-related genes

L-Ascorbic acid (AsA) is an important nutrient in non-heading Chinese cabbage (Brassica rapa ssp. chinensis). To understand the regulatory mechanism of AsA accumulation, we crossed "Wutacai" and "Erqing" to obtain F-2 plants and then constructed two pools (AsA-High and AsA-Low) of F-2-generation plants to further analyze the differentially expressed genes (DEGs) by cDNA-amplified fragment length polymorphism (cDNA-AFLP) technology. Among the DEGs, BcERF070 showed a significantly higher expression level in "Wutacai" and F-2 plants with high AsA than in "Erqing" and F-2 plants with low AsA, suggesting that BcERF070 is involved in the accumulation of AsA. To further understand the function of BcERF070 in AsA accumulation, we obtained BcERF070-silenced plants and BcERF070-overexpressed Arabidopsis thaliana plants. It was found that the downregulation of BcERF070 resulted in a decrease in AsA content, and the upregulation of BcERF070 resulted in an increase in AsA content. To evaluate the mechanism of BcERF070 involvement in the accumulation of AsA, the leaves of BcERF070-silenced and control plants were subjected to transcriptome sequencing. Twelve DEGs including BrAPXs were found to be associated with ascorbic acid. The qRT-PCR analysis on BcERF070-silenced plants and BcERF070-overexpressed plants further demonstrated the reliability of the transcriptome sequencing. Finally, based on analysis of the cis-acting elements of the promoter of 12 AsA-related genes, we speculated that BcERF070 may act on the DRE (dehydration-responsive element) of seven target gene promoters to regulate AsA content. In conclusion, a novel transcription factor, BcERF070, was revealed in this study, which affected the accumulation of AsA by regulating genes involved in the ascorbate biosynthesis and metabolic pathway. This information will help in understanding the regulatory mechanism of BcERF070 involvement in the accumulation of AsA in plants.