The MYB46/MYB83-mediated transcriptional regulatory programme is a gatekeeper of secondary wall biosynthesis

Abstract

Background: The secondary cell wall is a defining feature of xylem cells and allows them to resist both gravitational forces and the tension forces associated with the transpirational pull on their internal columns of water. Secondary walls also constitute the majority of plant biomass. Formation of secondary walls requires co-ordinated transcriptional regulation of the genes involved in the biosynthesis of cellulose, hemicellulose and lignin. This co-ordinated control appears to involve a multifaceted and multilayered transcriptional regulatory programme.

Scope: Transcription factor MYB46 (At5g12870) has been shown to function as a master regulator in secondary wall formation in Arabidopsis thaliana. Recent studies show that MYB46 not only regulates the transcription factors but also the biosynthesis genes for all of the three major components (i.e. cellulose, hemicellulose and lignin) of secondary walls. This review considers our current understanding of the MYB46-mediated transcriptional regulatory network, including upstream regulators, downstream targets and negative regulators of MYB46.

Conclusions and outlook: MYB46 is a unique transcription factor in that it directly regulates the biosynthesis genes for all of the three major components of the secondary wall as well as the transcription factors in the biosynthesis pathway. As such, MYB46 may offer a useful means for pathway-specific manipulation of secondary wall biosynthesis. However, realization of this potential requires additional information on the 'MYB46-mediated transcriptional regulatory programme', such as downstream direct targets, upstream regulators and interacting partners of MYB46.

Keywords: Arabidopsis thaliana; At5g12870; MYB46; Plant cell wall; biomass; secondary wall biosynthesis; transcription factor; transcriptional regulation.

Fig. 1.

MYB46/MYB83 function as a central regulator of secondary wall biosynthesis. Secondary wall biosynthesis is controlled by a complex and multifaceted transcriptional network including positive and negative feedback/forward regulation. Secondary wall NACs are upstream regulators of MYB46/MYB83, while several transcription factors are downstream targets. MYB46/MYB83 regulate the secondary wall biosynthesis genes either directly or co-operatively with downstream target transcription factors. Negative regulators are highlighted in red.