Degree Type


Date of Award


Degree Name

Master of Science


Genetics, Development and Cell Biology

First Advisor

Patrick S. Schnable


A variety of agricultural solutions are being tested to address the recent concern of rising rates of CO2 emissions, one of which is to engineer crops to increase their ability to store atmospheric carbon in soil. By targeting cell wall constituents of crop tissues with longer half-lives, such as lignin, the rate at which fixed CO2 in soil organic matter returns to the atmosphere becomes slowed. Maize is an attractive model organism for this approach, as it is grown worldwide, and has one of the most extensively catalogued plant genomes to date. The objective of this thesis is to provide a better understanding of the regulation of lignin composition and content i.e., genetic components that affect carbon storage in this model organism. This was approached by attempting to clone one of the brown midrib mutants of the phenylpropanoid pathway in maize, bm4. The objective was addressed by a fine-mapping approach, which helped to narrow the region of interest to a smaller interval suitable for cloning attempt. Identification and analysis of recombinants from 2 mapping populations segregating for brown midrib4 and wild-type alleles revealed an interval of 126,786 bp, encompassing 8 candidate genes. mRNA Seq transcriptome analyses of wild-type and mutant midrib tissues revealed transcript accumulation of > 40 reads for 4/8 genes within the interval. Further analysis revealed three of these 4 genes exhibit significant differential transcript accumulation between wild-type and mutant samples, with the greatest fold changes (1.92x) reported for a gene encoding the enzyme Folylpolyglutamate Synthetase (GRMZM2G393334). Transposon tagging was used to identify additional bm4 mutants. Cytological sections of midribs were stained and compared to explore subtle differences in mutants of different pedigrees. The continued characterization of bm4 in combination with other efforts to clone the genes underlying the brown midrib mutants will facilitate the understanding of their roles and functions in cell-wall composition, the biosynthesis of lignin, and potential for use in enhancing the carbon storage capabilities of maize tissues.


Copyright Owner

Danielle Elizabeth Reed



Date Available


File Format


File Size

69 pages