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J Integr Plant Biol, 58 (2): 136-149, Research Article
Characterization of novel Brown midrib 6 mutations affecting lignin biosynthesis in sorghum
Erin D. Scully1,2, Tammy Gries1, Deanna L. Funnell-Harris1,3, Zhanguo Xin4, Frank A. Kovacs5, Wilfred Vermerris6 and Scott E. Sattler1,2*
1Grain, Forage, and Bioenergy Research Unit, USDA-ARS, Lincoln, NE, USA
2Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE, USA
3Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, NE, USA
4Plant Stress and Germplasm Development Unit, USDA-ARS, Lubbock, TX, USA 5Department of Chemistry, University of Nebraska-Kearney, Kearney, NE, USA 6Department of Microbiology & Cell Science and UF Genetics Institute, University of Florida, Gainesville, FL, USA
*Correspondence:
E-mail: Scott.Sattler@ars.usda.gov
Abstract

The presence of lignin reduces the quality of lignocellulosic biomass for forage materials and feedstock for biofuels. In C4 grasses, the brown midrib phenotype has been linked to mutations to genes in the monolignol biosynthesis pathway. For example, the Bmr6 gene in sorghum (Sorghum bicolor) has been previously shown to encode cinnamyl alcohol dehydrogenase (CAD), which catalyzes the final step of the monolignol biosynthesis pathway. Mutations in this gene have been shown to reduce the abundance of lignin, enhance digestibility, and improve saccharification efficiencies and ethanol yields. Nine sorghum lines harboring five different bmr6 alleles were identified in an EMS-mutagenized TILLING population. DNA sequencing of Bmr6 revealed that the majority of the mutations impacted evolutionarily conserved amino acids while three-dimensional structural modeling predicted that all of these alleles interfered with the enzyme's ability to bind with its NADPH cofactor. All of the new alleles reduced in vitro CAD activity levels and enhanced glucose yields following saccharification. Further, many of these lines were associated with higher reductions in acid detergent lignin compared to lines harboring the previously characterized bmr6-ref allele. These bmr6 lines represent new breeding tools for manipulating biomass composition to enhance forage and feedstock quality.

 

Scully ED, Gries T, Funnell-Harris DL, Xin Z, Kovacs FA, Vermerris W, Sattler SE (2016) Characterization of novel Brown midrib 6 mutations affecting lignin biosynthesis in sorghum. J Integr Plant Biol 58: 136–149 doi: 10.1111/jipb.12375

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Received: 24 March 2015      Published: 14 July 2015
© 2016 Institute of Botany, Chinese Academy of Sciences
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