15-06: Identification and characterization of Cal-1, a high glucan maize mutant

In recent years plant cell walls and the polymers that constitute them have received increased attention as a potential highly abundant renewable resource for biofuel production. In particular, multiple members of the Poales order have been proposed as potential bioenergy feedstocks as they combine multiple desirable traits such as C4 photosynthesis, large biomass yield and fast growth. Examples include switchgrass, Miscanthus or sugar cane. Also crop residues like corn stover or wheat straw could be utilized.

We performed a forward genetic approach facilitating lignocellulosic wall sugar composition to identify mutants with alterations in their cell wall monosaccharide composition. Mutaganized lines of Zea mays (chemical mutagenesis) were analyzed and multiple lines with altered monosaccharide composition have been identified. In particular, one of the non-transgenic mutants termed candy-leaf 1 (Cal-1), was found to have a 246% increase in hemicellulosic glucan content in its leaves. Standard saccharification assays on leaf and stalk material demonstrated an increase in glucose yield of 34%. The reason for the underlying glucose increase has now been explained and we have been able to identifiy the single point mutation in the maize genome (total 2.5 billion base pairs) that leads to this high glucan phenotype in the lignocellulosics of Cal-1.