Transcriptional Activation of Secondary Wall Biosynthesis by Rice and Maize NAC and MYB Transcription Factors

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...

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Published in:	Plant and cell physiology Vol. 52; no. 10; pp. 1856 - 1871
Main Authors:	Zhong, Ruiqin, Lee, Chanhui, McCarthy, Ryan L., Reeves, Cromwell K., Jones, Evan G., Ye, Zheng-Hua
Format:	Journal Article
Language:	English
Published:	Japan Oxford University Press 01-10-2011
Subjects:	Acetylcysteine Arabidopsis 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 - 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 NAC Maize Secondary wall SWN Transcriptional regulation MYB46 Rice
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Summary:	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.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0032-0781 1471-9053
DOI:	10.1093/pcp/pcr123