MYB3 plays an important role in lignin and anthocyanin biosynthesis under salt stress condition in Arabidopsis

Abstract Salinity stress is one of the major factors in the reduction of plant growth and crop yield worldwide. To improve our ability to grow crops in high-salinity environments, plant responses to salinity stress must be tightly controlled. Here, in order to further understand the precise regulation of plant responses under high salinity conditions, the function of the MYB3 transcription factor was studied as a repressor to control excessive accumulation of lignin and anthocyanin under salt stress conditions. Nuclear-localized MYB3 forms a homodimer. It is ubiquitously expressed, especially in vascular tissues, and its expression is highly induced by NaCl in various tissues such as roots, leaves, stems, and flowers. myb3 mutant plants exhibited longer root growth in high NaCl conditions than wild-type plants. However, several NaCl responsive or signaling genes were not significantly altered in myb3 compared to wild-type. Interestingly, high accumulation of lignin and anthocyanin was displayed in myb3, and the expression of genes involved in lignin and anthocyanin biosynthesis, such as PAL1, C4H, COMT, 4CL3, DFR and LDOX, sharply increased in myb3 compared to those of wild-type plants under NaCl treatment. According to yeast-two hybrid screenings, various transcription factors, including anthocyanin regulators TT8 and EGL3, were isolated as MYB3 interacting proteins. MYB3 was characterized as a transcriptional repressor and its repressor domain is located in the C-terminus of MYB3. Overall, these results suggest that nuclear-localized MYB3 functions as a transcriptional repressor for the control of lignin and anthocyanin accumulation under salinity stress conditions.