ATL54, a ubiquitin ligase gene related to secondary cell wall formation, is transcriptionally regulated by MYB46

We previously characterized Arabidopsis Toxicos en Levadura54 (ATL54), a ubiquitin ligase associated with secondary cell wall formation. The ATL54 gene is co-expressed with secondary wall-associated genes, and the knock-out of ATL54 up-regulates the expression of cellulose, lignin, and xylan biosynthetic genes in apical stem portions of four-week-old plants. Here, we report the tissue-level localization patterns and the regulation of ATL54 expression. The beta-glucuronidase (GUS) reporter gene driven by the ATL54 promoter was significantly expressed in interfascicular fibers, xylary fibers, and vessels in inflorescence stems. A transient transfection assay using Arabidopsis T87 cells showed that the expression of the firefly luciferase gene driven by the ATL54 promoter was activated by MYB46, which is a key transcriptional activator of secondary wall formation. In addition, the electrophoretic mobility of ATL54 promoter fragments was shifted by a recombinant MYB46 protein. These results indicate that ATL54 expression is regulated by MYB46, and support the view that ATL54 has a role in secondary wall formation.