ZmMYB31 directly represses maize lignin genes and redirects the phenylpropanoid metabolic flux

Few regulators of phenylpropanoids have been identified in monocots having potential as biofuel crops. Here we demonstrate the role of the maize (Zea mays) R2R3-MYB factor ZmMYB31 in the control of the phenylpropanoid pathway. We determined its in vitro consensus DNA-binding sequence as ACCT/AACC, and chromatin immunoprecipitation (ChIP) established that it interacts with two lignin gene promoters in vivo. To explore the potential of ZmMYB31 as a regulator of phenylpropanoids in other plants, its role in the regulation of the phenylpropanoid pathway was further investigated in Arabidopsis thaliana. ZmMYB31 downregulates several genes involved in the synthesis of monolignols and transgenic plants are dwarf and show a significantly reduced lignin content with unaltered polymer composition. We demonstrate that these changes increase cell wall degradability of the transgenic plants. In addition, ZmMYB31 represses the synthesis of sinapoylmalate, resulting in plants that are more sensitive to UV irradiation, and induces several stress-related proteins. Our results suggest that, as an indirect effect of repression of lignin biosynthesis, transgenic plants redirect carbon flux towards the biosynthesis of anthocyanins. Thus, ZmMYB31 can be considered a good candidate for the manipulation of lignin biosynthesis in biotechnological applications.

This work was funded by the Spanish ‘Ministerio de Ciencia e Innovación’ (AGL2008-05157) to DCR, CGL2008-02470/BOS to AE and the CONSOLIDER-INGENIO program (CSD2007-00036) to PP, by the National Science Foundation Grant DBI-0701405 to JG and EG, Department of Energy grant DE-FG02-07ER15881 to EG and by an Ohio Plant Biotechnology Consortium Grant to JG and EG. SF was financed by a post-doctoral grant from the ‘Generalitat de Catalunya’ (2003PIV-A-00033) and by an I3P contract from the ‘Consejo Superior de Investigaciones Científicas’. DCR was financed by the Spanish ‘Ministerio de Educación y Ciencia’ (‘Ramón y Cajal’ and ‘I3’ Program). This work was carried out within the framework of the ‘Xarxa de Referència de Biotecnologia’ (XarBa) from the Autonomous Government of Catalonia.

Peer reviewed