The transcription factor MYB115 contributes to the regulation of proanthocyanidin biosynthesis and enhances fungal resistance in poplar

Proanthocyanidins (PAs) are major defense phenolic compounds in the leaves of poplar (Populus spp.) in response to abiotic and biotic stresses. Transcriptional regulation of PA biosynthetic genes by the MYB-basic helix-loop-helix (bHLH)-WD40 complexes in poplar is not still fully understood. Here, an Arabidopsis TT2-like gene MYB115 was isolated from Populus tomentosa and characterized by various molecular, genetic and biochemical approaches. MYB115 restored PA productions in the seed coat of the Arabidopsis tt2 mutant. Overexpression of MYB115 in poplar activated expression of PA biosynthetic genes, resulting in a significant increase in PA concentrations. By contrast, the CRISPR/Cas9-generated myb115 mutant exhibited reduced PA content and decreased expression of PA biosynthetic genes. MYB115 directly activated the promoters of PA-specific structural genes. MYB115 interacted…