Both for cattle nutrition and biofuel production, the improvement in maize (Zea mays L.) cell wall degradability depends on understanding the genetic mechanisms involved in the biosynthesis of phenylpropanoids. Most of the genes involved in monolignol and p‐hydroxycinnamate biosynthesis are known, but many belong to multigene families. A macro‐array with cell wall gene specific tags was used to characterize the different gene expression profiles in maize ear internode at four stages from 7 d before silking to 15 d after silking. Gene expression profiles were related to biochemical variation observed for lignin content, lignin structure, and esterified and etherified ferulic acid content. Most of the significantly expressed genes had a maximum at the first stages of sampling with their expression decreasing rapidly thereafter. A few genes had a second later expression peak. In each multigene family, only a restricted number of genes were expressed during maize cell wall formation in the below‐ear internode. Genes for three phenylalanine ammonia‐lyases, two cinnamate 4‐hydroxylases, two 4‐coumarate:coenzyme A ligases, three caffeoyl‐CoA O‐methyltransferases, but only one cinnamoyl‐CoA reductase, two cinnamyl alcohol dehydrogenases, one ferulate 5‐hydroxylase, the only caffeic acid O‐methyltransferase, and a ZRP4‐like O‐methyltransferase were significantly expressed. These genes are likely the most important ones in maize stem lignification, and hence are priority targets in maize breeding.

Grasses, which are currently at the basis of cattle feeding, will, in the near future, be a major source of cell wall carbohydrates for sustainable biofuel production. The association of lignins with other matrix components, together with linkages between cell wall carbohydrates, greatly influences cell wall properties, including the degradability of structural polysaccharides by micro-organisms in animal rumen or industrial fermenters. The improvement in biofuel production from plants is based on the understanding of the cell wall composition and assembly, and on the discovery of genetic and genomic mechanisms involved in each component biosynthesis and their depositions in each lignified tissue. While nearly 40 QTL have been shown for lignin content, only seven locations appeared of greater importance in investigated genetic resources. Expression studies highlighted that several genes in the lignin pathway are less expressed in lines with higher cell wall degradability. However, only a few lignin pathway genes mapped in QTL positions, and the fully relevant candidates might be genes involved in regulation of lignin pathway genes, or in regulation of lignified tissue assembly.