ARS | Publication request: Reduction of ferulate ether cross links in maize stover due to selection for low ferulate ester concentrations in seedlings improves cell wall digestibility

Submitted to: Meeting Abstract
Publication Type: Abstract
Publication Acceptance Date: July 1, 2008
Publication Date: August 25, 2008
Citation: Jung, H.G., Phillips, R.L. 2008. Reduction of ferulate ether cross links in maize stover due to selection for low ferulate ester concentrations in seedlings improves cell wall digestibility [abstract]. Ferulate '08 An International Conference on Hydroxycinnamates and Related Plant Phenolics Proceedings, August 25-27, 2008, Minneapolis, Minnesota. p. 35.

Technical Abstract: We hypothesized that ferulate-mediated cross links between lignin and hemicellulose in the cell walls of grasses could be reduced by inhibition of ferulate ester biosynthesis. Further, a reduction in cross linking should lead to improved digestibility of cell wall polysaccharides. We report here that a putative mutant in maize with reduced ferulate ester concentrations in seedling leaves resulted in reduced ferulate ether (cross link) concentrations in stover at silage maturity and improved in vitro rumen fiber digestibility. The putative maize seedling ferulate ester (sfe) mutant was identified from a transposon mutagenesis population as having an approximately 50% lower concentration of ferulate esters. Four near-isogenic backcross-4 lines were created from the original putative mutant plant and compared to the parental inbred line in a replicated field study conducted at two locations in 2005 and 2006. Ferulate ester concentrations of the first true leaf of maize seedlings, collected when the third leaf was emerging from the leaf whorl, were lower (15%) for only two of the four sfe isolines than the parental inbred. The sfe isolines did not differ from the parental inbred in height or internode number at silking, but internode cross-sectional area was larger (7%) for the sfe isolines. Total silage yield was higher (8%) for the sfe isolines, with increased stem proportion (29%) accounting for this difference. Silage stage stover of the maize lines was separated into leaf blade, sheath, and stem fractions for chemical analysis. For all three plant parts, the sfe isolines had lower concentrations of ferulate ethers (-15, -10, and -19% for blades, sheaths, and stems, respectively) than the parental inbred, but concentrations of ferulate esters were not different. Acid detergent lignin concentration was similar among sfe isolines and the parental inbred for leaf blades, but lower for sheaths (-5%) and stems (-14%). In vitro digestibility of neutral detergent fiber by a mixed rumen inoculum was greater for leaf blade, sheath, and stem plant parts than the parental inbred after both 24-h (9, 13, and 14%, respectively) and 96-h (4, 6, and 8%, respectively) incubations. Additional data on cell wall concentration, composition, and in vitro digestibility will be presented. These data support our hypothesis that reducing ferulate ester biosynthesis will result in formation of fewer ferulate-mediated cross links of lignin to hemicellulose, and that this reduced cross linking will improve cell wall digestibility. We expect that conversion of the sfe mutant maize to cellulosic ethanol will also be enhanced.