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The article presents information about beta glucan, an enzyme that synthesizes a polysaccharide in plant cell walls. It is a major cell wall component in grains, including the barleys used in brewing. Its presence can not only negatively affect fermentation, but can also inhibit the filtration process, leaving beer with an unappealing haze. Thus, it is not surprising that plant breeders have sought to identify the genes that determine how much beta glucan is produced in barley. A region of genomic DNA that controls the production of this polysaccharide in barley grains has been mapped to chromosome 2. To identify the genes and proteins responsible for beta glucan biosynthesis, some researchers have taken advantage of this information and the conserved genome structure between barley and rice, whose genome has been completely sequenced. The cellulose synthase like genes were first identified in the model plant Arabidopsis thaliana and rice genomes. Sequence analyses indicate that the cellulose synthase superfamily contains multiple subfamilies.