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Title: Divergent selection for ester-linked diferulates in maize pith stalk tissues: effects on cell wall composition and degradability

Author
item BARROS-RIOS, JAIME - Biological Mission Of Galicia Spain
item MALVAR, ROSA - Biological Mission Of Galicia Spain
item Jung, Hans Joachim
item BUNZEL, MIRKO - University Of Minnesota
item SANTIAGO, ROGELIO - Biological Mission Of Galicia Spain

Submitted to: Phytochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/30/2012
Publication Date: 8/30/2012
Citation: Barros-Rios, J., Malvar, R.A., Jung, H.G., Bunzel, M., Santiago, R. 2012. Divergent selection for ester-linked diferulates in maize pith stalk tissues. Effects on cell wall composition and degradability. Phytochemistry. 83:43-50.

Interpretive Summary: Recently it was demonstrated that corn plants with increased amounts of cross linking between cells by a specific compound known as diferulates were more resistant to corn borer attack, a major insect pest of corn. A study was done to determine if the amount of diferulates in corn was a heritable trait that could be used to provide a non-GMO resistance to corn by conventional breeding methods. After two generations of selection for either higher or lower amounts of diferulates, corn lines were developed that differed significantly in their diferulate content, demonstrating that diferulate content can be modified by conventional breeding. However, the stover from corn lines with more diferulates was less digestible by bacteria from the rumen of cows in a laboratory test than corn lines with less diferulates. These results indicate that natural corn borer resistance by diferulates could be improved through breeding for corn varieties intended for grain production but may have less value in varieties bred for use as whole corn plant silage to be fed to cattle.

Technical Abstract: Cross-linking of grass cell wall components through diferulates (DFAs) has a marked impact on cell wall properties. However, results of genetic selection for DFA concentration have not been reported for any grass species. We report here the results of direct selection for ester-linked DFA concentration in maize stalk pith tissues and the associated changes in cell wall composition and biodegradability. After two cycles of divergent selection, maize populations selected for higher total DFA (DFAT) content (CHs) had 16% higher DFAT concentrations than populations selected for lower DFAT content (CLs). These significant DFA concentration gains suggest that DFA deposition in maize pith parenchyma cell walls is a highly heritable trait that is genetically regulated and can be modified through conventional breeding. Maize populations selected for higher DFAT had 13% less glucose and 10% lower total cell wall concentration than CLs, suggesting that increased cross-linking of feruloylated arabinoxylans results in repacking of the matrix and possibly in thinner and firmer cell walls. Divergent selection affected esterified DFAT and monomeric ferulate ether cross link concentrations differently, supporting the hypothesis that the biosynthesis of these cell wall components are separately regulated. As expected, a more higher DFA ester cross-coupled arabinoxylan network had an effect on rumen cell wall degradability (CLs showed 12% higher 24-h total polysaccharide degradability than CHs). Interestingly, 8-8-coupled DFAs, previously associated with cell wall strength, were the best predictors of pith cell wall degradability (negative impact). Thus, further research on the involvement of these specific DFA regioisomers in limiting cell wall biodegradability is encouraged.