| dc.description.abstract |
<p>The Arabidopsis root apical meristem (RAM) is a complex tissue capable of generating
all the cell types that ultimately make up the root. The work presented in this thesis
takes advantage of the versatility of high-throughput sequencing to address two independent
questions about the root meristem. Although a lot of information is known regarding
the cell fate decisions that occur at the RAM, cortex specification and differentiation
remain poorly understood. In the first part of this thesis, I used an ethylmethanesulfonate
(EMS) mutagenized marker line to perform a forward genetics screen. The goal of this
screen was to identify novel genes involved in the specification and differentiation
of the cortex tissue. Mapping analysis from the results obtained in this screen revealed
a new allele of BRASSINOSTEROID4 with abnormal marker expression in the cortex tissue.
Although this allele proved to be non-cortex specific, this project highlights new
technology that allows mapping of EMS-generated mutations without the need to map-cross
or back-cross. In the second part of this thesis, using fluorescence activated cell
sorting (FACS) coupled with high throughput sequencing, my collaborators and I generated
single-base resolution whole genome DNA methylomes, mRNA transcriptomes, and smallRNA
transcriptomes for six different populations of cell types in the Arabidopsis root
meristem. We were able to discover that the columella is hypermethylated in the CHH
context within transposable elements. This hypermethylation is accompanied by upregulation
of the RNA-dependent DNA methylation pathway (RdDM), including higher levels of 24-nt
silencing RNAs (siRNAs). In summary, our studies demonstrate the versatility of high-throughput
sequencing as a method for identifying single mutations or to perform complex comparative
genomic analyses.</p>
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