Date Approved

2012

Degree Type

Open Access Senior Honors Thesis

Department

Biology

First Advisor

Aaron Liepman

Second Advisor

Marianne Laporte

Abstract

Plant cell walls are the world's most abundant source of renewable biomass. Consisting mainly of carbohydrates, including mannans, plant cell walls are vital to humanity as a source of food, health products, and biofuels. Previous research suggests diverse functions of mannans and implicates several members of the CELLULOSE SYNTHASE-LIKE A (CSLA) gene family as mannan synthases, proteins involved in mannan backbone synthesis. Prior research using Arabidopsis thaliana (A. thaliana) cs/a single mutants showed no obvious phenotypic abnormalities, with the exception of cs/a7, which was embryo lethal; however, ectopic expression of CSLA9 complemented the csla7 mutant phenotype, suggesting csla7 and csla9 enzymes make similar carbohydrate products. Additionally, an -81% reduction in inflorescence stem glucomannan content, reduced quantity and growth rate of lateral roots, as well as a reduced susceptibility to Agrobacterium tumefaciens-mediated transformations have been observed in csla9 knockout mutants. Questions regarding the specific biological functions of CSLA proteins await further investigation. Thus, it was hypothesized in A. thaliana, AtCSLAl and AtCSLA9 have unique expression patterns in various tissues during specific stages of development. The expression patterns of the AtCSLA7 and AtCSLA9 genes during plant development were studied in A. thaliana using promoter-GUS fusion analysis. The results demonstrated unique expression patterns of the AtCSLA7 and AtCSLA9 genes, with numerous examples of overlapping expression at specific developmental stages, supporting the hypothesis. Understanding AtCSLA7 and AtCSLA9 gene expression patterns and functions will also improve understanding of the roles of mannan carbohydrates in plants.

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