PMID:21908441

Citation	Zhong, R, Lee, C, McCarthy, RL, Reeves, CK, Jones, EG and Ye, ZH (2011) Transcriptional activation of secondary wall biosynthesis by rice and maize NAC and MYB transcription factors. Plant Cell Physiol. 52:1856-71
Abstract	The bulk of grass biomass potentially useful for cellulose-based biofuel production is the remains of secondary wall-containing sclerenchymatous fibers. Hence, it is important to uncover the molecular mechanisms underlying the regulation of secondary wall thickening in grass species. So far, little is known about the transcriptional regulatory switches responsible for the activation of the secondary wall biosynthetic program in grass species. Here, we report the roles of a group of rice and maize NAC and MYB transcription factors in the regulation of secondary wall biosynthesis. The rice and maize secondary wall-associated NACs (namely OsSWNs and ZmSWNs) were able to complement the Arabidopsis snd1 nst1 double mutant defective in secondary wall thickening. When overexpressed in Arabidopsis, OsSWNs and ZmSWNs were sufficient to activate a number of secondary wall-associated transcription factors and secondary wall biosynthetic genes, and concomitantly result in the ectopic deposition of cellulose, xylan and lignin. It was also found that the rice and maize MYB transcription factors, OsMYB46 and ZmMYB46, are functional orthologs of Arabidopsis MYB46/MYB83 and, when overexpressed in Arabidopsis, they were able to activate the entire secondary wall biosynthetic program. Furthermore, the promoters of OsMYB46 and ZmMYB46 contain secondary wall NAC-binding elements (SNBEs), which can be bound and activated by OsSWNs and ZmSWNs. Together, our results indicate that the rice and maize SWNs and MYB46 are master transcriptional activators of the secondary wall biosynthetic program and that OsSWNs and ZmSWNs activate their direct target genes through binding to the SNBE sites.
Links	PubMed Online version:10.1093/pcp/pcr123
Keywords	Arabidopsis/genetics; Arabidopsis/metabolism; Arabidopsis Proteins/metabolism; Base Sequence; Cell Wall/genetics; Cell Wall/metabolism; Gene Expression Regulation, Plant; Genes, Plant; Genetic Complementation Test; Mutation/genetics; Oryza sativa/genetics; Phylogeny; Plant Epidermis/cytology; Plant Epidermis/metabolism; Plant Proteins/chemistry; Plant Proteins/metabolism; Plants, Genetically Modified; Promoter Regions, Genetic/genetics; Protein Binding; Protein Structure, Tertiary; Sequence Homology, Amino Acid; Transcription Factors/chemistry; Transcription Factors/metabolism; Transcriptional Activation/genetics; Zea mays/genetics
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
MAIZE:G3M8E6		GO:0006355: regulation of transcription, DNA-dependent	ECO:0000316:	UniProtKB:Q9LXV2	P		Fig. 7	complete
MAIZE:B4FVL2		GO:0006355: regulation of transcription, DNA-dependent	ECO:0000316:	UniProtKB:Q9LPI7	P		Figure 11: ZmSWN6 is capable of activating the Arabidopsis SNBE promoter of AtMYB46	complete
MAIZE:B4FVL2		GO:2000652: regulation of secondary cell wall biogenesis	ECO:0000316:	UniProtKB:Q9LPI7	P		Figure 9: Overexpression of ZmSWN6 causes deposition of cellulose, lignin, and xylan in Arabidopsis secondary cell walls	complete

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