Overexpression of the LoMYB29 gene of Larix olgensis contributes to the regulation of proanthocyanidin biosynthesis in Arabidopsis thaliana

Abstract

Proanthocyanidins (PAs) are the most broadly distributed secondary metabolites that play important roles in various aspects of plant development and response to biotic and abiotic stresses. In this study, we cloned a R2R3 MYB gene LoMYB29, which has a full-length coding sequence of 921 bp identified in Larix olgensis. Quantitative real-time reverse transcription polymerase chain reaction analysis indicates that LoMYB29 is expressed under mechanical wounding, high light intensity, and NaCl, PEG6000, Methyl Jasmonate, and abscisic acid treatments. Subcellular localization analysis and yeast two-hybrid assay localized LoMYB29 to the nucleus, acting as a transcriptional activator. Staining with 4-dimethylaminocinnamaldehyde showed a darker blue-purple color in LoMYB29-overexpressing Arabidopsis seeds compared to that of wild seeds. LoMYB29-overexpression resulted in a significant increase in leaf PA content. The expression of early flavonoid biosynthesis-related gene CHI and late flavonoid biosynthesis-related genes, including DFR, LDOX, and ANR (PA branch gene), were also activated in transgenic plants overexpressing LoMYB29. The results indicate that LoMYB29 plays a positive role in the regulation of PA biosynthesis by activating the expression of PA biosynthetic genes.