Maize cell wall genes identified, giving boost to biofuel research

The Purdue scientists, led by Nicholas Carpita, a professor of plant cell biology, published their findings on the 750 cell wall genes in the journal Plant Physiology on Thursday (Nov. 19). They also were co-authors on a study, published Thursday (Nov. 19) in Science, that for the first time sequenced the genome of maize.

In discovering the some 32,000 genes of maize, scientists can better study the function of individual genes and how each affects all aspects of the plant's development. Purdue's scientists are particularly interested in the genes that regulate cellulose, lignin and other parts of plant's cell walls.

"This gives us an inventory of the genes that could become possible targets for modification in the production of biomass," Carpita said. "We want to be able to control the structure of the cell walls."

Carpita and Maureen McCann, a professor of biology and a co-author on both papers, are part of Purdue's C3Bio research project, which is aimed at using thermal and chemical catalysts to create biofuels that utilize more of a plant's carbon. The team hopes to engineer catalysts or catalytic sites into plants and use heat or chemical catalysts to directly convert the biomass into fuel.

"The grasses, including maize, make a unique kind of cell wall," Carpita said. "Beyond the cell wall genes, having a complete genome will enable us to identify developmental controls, such as genes that delay flowering to continue production of biomass, or alter pathways so that plants accumulate more sugar in the stem."

The annotation of the maize cell wall genes also led to the discovery of more than 80 mutants involved in cell wall production. Scientists can grow plants that have a gene mutation and compare them to those without the mutation to understand how changes in the gene functions in biomass accumulation or quality in maize.

"Discovering the genome sequence of maize is a huge step forward in getting at the functions of genes that will be useful in developing new bioenergy crops," McCann said. "We will be able to identify mutants in key genes of interest and then assess how mutation changes the plant cell wall and if those changes are useful."

Researchers found that maize's cell wall genes were more similar to those of rice than to Arabidopsis, a plant often used as a model in scientific experiments.

"Now we're starting to see differences in the families of related genes and how those genes are expressed," said Bryan Penning, McCann's lab manager and a co-author on both papers. "Now that we have the sequence, we can start building a reservoir of data on the expression patterns of the cell wall genes."

The next step in using the data collected will include testing the mutant genes and exploring how expression of particular genes can be regulated to produce desired characteristics in a maize plant.

Other Purdue scientists involved in the Science paper were Phillip San Miguel, director of the Agricultural Genomics Center, and Richard Westerman, a systems manager and senior programmer in horticulture and landscape architecture. Purdue researchers collaborated with the University of Florida and the National Renewable Energy Laboratory.