Arabidopsis MYB47 and MYB95 transcription factors regulate jasmonate-inducible ER-body formation

Abstract

Endoplasmic reticulum (ER)-derived subcellular structures, namely ER bodies, are involved in glucosinolate-based chemical defense against insect pests and pathogenic fungi in the Brassicaceae family. In Arabidopsis thaliana, treatment of rosette leaves with the wounding hormone jasmonate (JA) induces β-GLUCOSIDASE 18 (BGLU18) and TSK-ASSOCIATING PROTEIN 1 (TSA1) gene expression, whose products accumulate in JA-inducible ER bodies; however, the underlying transcriptional regulatory mechanisms remain unknown. Here, we show that two paralogous Arabidopsis MYBs, namely MYB47 and MYB95, regulate TSA1 and BGLU18 expression and ER-body formation in response to JA. MYB47 and MYB95 bind to and activate the TSA1 promoter. TSA1 and BGLU18 expression levels are reduced in the JA-treated rosette leaves of myb47,95 mutants, suggesting that these MYBs play a key role in the activation of these genes. Transcriptome analysis reveals that MYB47 and MYB95 regulate a subset of JA-responsive genes, including ER-body and defense-related genes. Phylogenetic analysis shows that MYB47 and MYB95 belong to a MYB subfamily unique to the Brassicales order. Together, our findings indicate that MYB47 and MYB95 have evolved to regulate unique downstream target genes in response to JA, which include JA-inducible ER body genes important for protecting plants from fungal and herbivore attacks in Brassicaceae.