Genetic Resources for Maize Cell Wall Biology      

Abstract

Grass species represent a major source of food, feed, and fiber crops and potential feedstocks for biofuel production. Most of the biomass is contributed by cell walls that are distinct in composition from all other flowering plants. Identifying cell wallrelated genes and their functions underpins a fundamental understanding of growth and development in these species. Toward this goal, we are building a knowledge base of the maize (Zea mays) genes involved in cell wall biology, their expression profiles, and the phenotypic consequences of mutation. Over 750 maize genes were annotated and assembled into gene families predicted to function in cell wall biogenesis. Comparative genomics of maize, rice (Oryza sativa), and Arabidopsis (Arabidopsis thaliana) sequences reveal differences in gene family structure between grass species and a reference eudicot species. Analysis of transcript profile data for cell wall genes in developing maize ovaries revealed that expression within families differed by up to 100-fold. When transcriptional analyses of developing ovaries before pollination from Arabidopsis, rice, and maize were contrasted, distinct sets of cell wall genes were expressed in grasses. These differences in gene family structure and expression between Arabidopsis and the grasses underscore the requirement for a grass-specific genetic model for functional analyses. A UniformMu population proved to be an important resource in both forward-and reverse-genetics approaches to identify hundreds of mutants in cell wall genes. A forward screen of field-grown lines by near-infrared spectroscopic screen of mature leaves yielded several dozen lines with heritable spectroscopic phenotypes. Pyrolysismolecular beam mass spectrometry confirmed that several nir mutants had altered carbohydrate-lignin compositions.

The Maize Mixed-Linkage (1→3),(1→4)-β-d-Glucan Polysaccharide Is Synthesized at the Golgi Membrane

“…Mutants with severely modified xyloglucans altered in their ability to be recognized by XETs resulted in loss of tensile strength of the hypocotyl, indicating that the enzyme is necessary to retether the long interstitial xyloglucans during microfibril rearrangment and formation of new partners (Peñ a et al, 2004). Because the xyloglucan endo-b-transglucosylase/hydrolase gene family is quite large in what are considered xyloglucanpoor grass species (Yokoyama et al, 2004;Penning et al, 2009), other substrates were considered for its disproportioning activity that could increase polymer length or make covalently linked heteropolymers (Hrmova et al, 2007). In light of the inability to detect b-glucans in the Golgi membrane, Fincher (2009) Hrmova et al (2007) was catalyzed at quite reasonable rates, it should be noted that those activities were about 1/500 the rate of xyloglucan transglucosylation.…”

Genetic Determinants for Enzymatic Digestion of Lignocellulosic Biomass Are Independent of Those for Lignin Abundance in a Maize Recombinant Inbred Population

“…In some families, a substantially higher number of duplicates were found. For example, all duplicates of the 10 cellulose synthase CesA family members were retained (Penning et al, 2009). Because conventional algorithms only map sequences to unique genes, the high degree of duplication in maize led to an unexpectedly large number of unmapped sequences.…”

Transcriptional dynamics during cell wall removal and regeneration reveals key genes involved in cell wall development in rice

“…Rice snl6 and Arabidopsis irx4 mutants, defective in CCR encoding genes, display altered lignin composition Bart et al 2010). HCT catalyzes generation of p-coumaroyl-CoA from p-coumaric acid and transfer of caffeoyl moiety of caffeoyl-quinate and caffeoyl-shikimate to CoA (Hoffmann et al 2003;Penning et al 2009). …”

“…Nucleotide-sugar interconversion pathway Genes involved in nucleotide-sugar interconversion pathway form the basic building blocks of cell wall carbohydrates (Penning et al 2009;Seifert et al 2004). We found that three genes, belonging to each of three groups of C-4 epimerases including GAE-like (UDP-glucuronate-4-epimerase; LOC_Os08g41440), UXE-like (GDP-mannose 4,6-dehydratase; LOC_Os07g04690) and UGE-like (UDPglucose-4-epimerase; LOC_Os09g35800) were up-regulated during cell wall removal (Table 1).…”