Overexpression of SbMyb60 impacts phenylpropanoid biosynthesis and alters secondary cell wall composition in Sorghum bicolor. (30th January 2016)

• Record Type: Journal Article
• Authors: Scully, Erin D.; Gries, Tammy; Sarath, Gautam; Palmer, Nathan A.; Baird, Lisa; Serapiglia, Michelle J.; Dien, Bruce S.; Boateng, Akwasi A.; Ge, Zhengxiang; Funnell‐Harris, Deanna L.; Twigg, Paul; Clemente, Thomas E.; Sattler, Scott E.
• Is Part Of: Plant journal. Volume 85:Number 3(2016:Feb.)
• Page Start: 378
• Page End: 395
• Publication Date: 2016-01-30
• Subjects: lignin -- monocot -- monolignol -- C4 grass -- bioenergy -- transgenic; Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.13112
• Languages: English
• ISSNs: 0960-7412

Abstract

Summary: The phenylpropanoid biosynthetic pathway that generates lignin subunits represents a significant target for altering the abundance and composition of lignin. The global regulators of phenylpropanoid metabolism may include MYB transcription factors, whose expression levels have been correlated with changes in secondary cell wall composition and the levels of several other aromatic compounds, including anthocyanins and flavonoids. While transcription factors correlated with downregulation of the phenylpropanoid biosynthesis pathway have been identified in several grass species, few transcription factors linked to activation of this pathway have been identified in C4 grasses, some of which are being developed as dedicated bioenergy feedstocks. In this study we investigated the role of SbMyb60 in lignin biosynthesis in sorghum ( Sorghum bicolor ), which is a drought‐tolerant, high‐yielding biomass crop. Ectopic expression of this transcription factor in sorghum was associated with higher expression levels of genes involved in monolignol biosynthesis, and led to higher abundances of syringyl lignin, significant compositional changes to the lignin polymer and increased lignin concentration in biomass. Moreover, transgenic plants constitutively overexpressing SbMyb60 also displayed ectopic lignification in leaf midribs and elevated concentrations of soluble phenolic compounds in biomass. Results indicate that overexpression of SbMyb60 is associated with activation of monolignol biosynthesis in sorghum. SbMyb60 represents a target for modification of plant cell wall composition, with the potential to improve biomass for renewable uses. Significance Statement: Reducing lignin in cell walls is desirable for biofuel applications. Few positive transcriptional regulators of lignin biosynthesis have been identified in monocot grasses. Here we show that overexpression of SbMyb60 stimulates expression of genes in the monolignol biosynthesis pathway, resulting in ectopic lignin in leaves, altered cell wall composition, and increased soluble phenolic compounds in biomass. Thus SbMyb60 represents a new target for modifying cell wall composition in sorghum and other monocots.