Abstract
BackgroundOMT (O-methyltransferase) genes are involved in lignin biosynthesis, which relates to stover cell wall digestibility. Reduced lignin content is an important determinant of both forage quality and ethanol conversion efficiency of maize stover.ResultsVariation in genomic sequences coding for COMT, CCoAOMT1, and CCoAOMT2 was analyzed in relation to stover cell wall digestibility for a panel of 40 European forage maize inbred lines, and re-analyzed for a panel of 34 lines from a published French study. Different methodologies for association analysis were performed and compared. Across association methodologies, a total number of 25, 12, 1, 6 COMT polymorphic sites were significantly associated with DNDF, OMD, NDF, and WSC, respectively. Association analysis for CCoAOMT1 and CCoAOMT2 identified substantially fewer polymorphic sites (3 and 2, respectively) associated with the investigated traits. Our re-analysis on the 34 lines from a published French dataset identified 14 polymorphic sites significantly associated with cell wall digestibility, two of them were consistent with our study. Promising polymorphisms putatively causally associated with variability of cell wall digestibility were inferred from the total number of significantly associated SNPs/Indels.ConclusionsSeveral polymorphic sites for three O-methyltransferase loci were associated with stover cell wall digestibility. All three tested genes seem to be involved in controlling DNDF, in particular COMT. Thus, considerable variation among Bm3 wildtype alleles can be exploited for improving cell-wall digestibility. Target sites for functional markers were identified enabling development of efficient marker-based selection strategies.
Highlights
OMT (O-methyltransferase) genes are involved in lignin biosynthesis, which relates to stover cell wall digestibility
Variation in genomic sequences coding for caffeic acid Omethyltransferase (COMT), CCoAOMT1, and CCoAOMT2 was analyzed in relation to stover cell wall digestibility for the same panel of 40 European forage maize inbred lines investigated by Andersen et al [38,42] for other “lignin genes” (Experiment 1)
digestible Neutral Detergent Fiber (DNDF) was estimated by DNDF = 100 (IVDMD - (100 - Neutral Detergent Fiber (NDF)))/NDF based on Goering and Van Soest, 1970 [43]
Summary
OMT (O-methyltransferase) genes are involved in lignin biosynthesis, which relates to stover cell wall digestibility. Reduced lignin content is an important determinant of both forage quality and ethanol conversion efficiency of maize stover. Stover cell-wall digestibility has long been shown to be crucial for forage quality, and more recently this trait is getting more attention in relation to biofuel production. Reduced lignin content improves cell wall digestibility due to increased accessibility of cellulose and hemicelluloses by enzymatic procedures, enabling better ethanol conversion efficiency [4]. Lignins are phenolic polymers resulting from three monolignols: p-coumaryl, coniferyl, and sinapyl alcohol. These monolignols derive p-hydroxyphenyl H, guaiacyl G, and syringyl S phenylpropanoid units, respectively, which polymerize by oxidation to form lignins [5]. Lignins are predominantly comprised of G and S units (37.5 and 60.0%, respectively) [6], with a low, but noticeable content in H units which is nearly five times higher than in dicotyledonous plants
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