|SABALLOS, ANA - University Of Florida
|VERMERRIS, WILFRED - University Of Florida
Submitted to: Genes, Genomes, Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2014
Publication Date: 11/1/2014
Publication URL: http://www.g3journal.org/content/4/11/2115.full.pdf+html
Citation: Sattler, S.E., Saballos, A., Xin, Z., Funnell-Harris, D.L., Vermerris, W., Pedersen, J.F. 2014. Characterization of novel sorghum brown midrib mutants from an EMS-mutagenized population. Genes, Genomes, Genetics. 4: 2115-2124. DOI: 10.1534/g3.114.014001.
Interpretive Summary: In the US, sorghum biomass (stalks and leaves) serves as an important forage crop for livestock. In addition, sorghum is being developed as a bioenergy crop for cellulosic biofuels. Cellulosic biofuels are derived from the breakdown of the cell wall components (cellulose and hemicellulose) of the biomass to sugars and the conversions of these sugars to fuel molecules. A third cell wall component, lignin, makes cell walls resistant to breakdown into sugars. In sorghum, brown midrib (bmr) mutants are a class of mutants, known to reduce lignin content in plant cell walls. These mutants have been used to develop plant varieties with reduced lignin, which have led to improved bioenergy conversion and increased livestock digestibility. In this study, we identified six new bmr mutants, which are different from the previously identified bmr mutants. We characterized the effects these new mutants had on lignin content and the ability to digest cell walls into sugars. These mutants provide scientists with new tools to improve sorghum biomass for bioenergy and forage, and will potentially aid the identification of genes controlling lignin synthesis in sorghum and other bioenergy grasses.
Technical Abstract: Reducing lignin concentration in lignocellulosic biomass can increase forage digestibility for ruminant livestock and saccharification yields of biomass for bioenergy. In sorghum (Sorghum bicolor (L.) Moench) and several other C4 grasses, brown midrib (bmr) mutants have been shown to reduce lignin concentration. Forty-six putative bmr mutants isolated from an EMS-mutagenized population were characterized and classified based upon their midrib leaf phenotype and allelism tests with the previously described sorghum bmr loci bmr2, bmr6 and bmr12. These tests resulted in the identification of additional alleles of bmr2, bmr6 and bmr12, and in addition, six bmr mutants were identified that were not allelic to these previously described loci. Further allelism testing amongst these six bmr mutants showed that they represented four previously undescribed bmr loci. Based on this study the number of bmr loci uncovered in sorghum has doubled. The impact of these lines on agronomic traits and lignocellulosic composition was assessed in a two-year field study. Overall, most of the identified bmr lines showed reduced lignin concentration of their biomass relative to wild-type. Effects of the six new bmr mutants on enzymatic saccharification of lignocellulosic materials were determined, but the amount of glucose released from the stover was similar to WT in all cases. These mutants may affect monolignol biosynthesis, similar to bmr2, bmr6 and bmr12, and through stacking these mutants together or in combination with the three previously described loci may be useful for bioenergy and forage improvement.