Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Biology

Supervisor

Mark A. Bernards

2nd Supervisor

Isabel Molina

Affiliation

Algoma University

Co-Supervisor

Abstract

Suberin is a complex polymer comprising an aliphatic polyester and an aromatic polymer, co-deposited with soluble waxes. The aliphatic polyester is composed of fatty acids, ω-hydroxy fatty acids, α,ω-dicarboxylic acids, fatty alcohols, glycerol, and ferulate. In potato, alkyl ferulates, are a major component of suberin-associated waxes. The lignin-like aromatic polymer is comprised of hydroxycinnamic acids and monolignols. Members of the HXXXD/BAHD acyltransferase family are required for the biosynthesis of the aliphatic suberin polyester and suberin-associated waxes, but their possible role in the biosynthesis of the phenolic domain of suberin remains unexplored. Here I studied the function of three BAHD candidate genes (StFHT and StFACT and St430) in the formation of the poly(phenolic) domain of suberin by characterization of wound-induced suberization in tubers from RNAi-knockdown lines. Overall, my results indicated that these genes may not function in the biosynthesis of the phenolic domain of suberin.

Summary for Lay Audience

Plants make suberin to control water and nutrient loss and to build a physical barrier against infectious agents such as viruses and bacteria. Suberin is an impermeable polymer that acts as a barrier between underground parts of plants and the environment. Wound healing also elicits the production of new suberized cell layers in plants. These suberized cells provide protection to the internal plant tissues exposed by wounding. This process is similar to the wound healing process in human skin where scabs develop to seal the wounded area and protect the internal tissues. Suberin is found in the cell wall of underground plant tissues such as the potato tuber skin, and in aboveground tissues like the bark of trees. One extreme example is that of the cork oak tree that has a very thick suberized bark layer that is sustainably harvested for the cork production. Understanding the function of suberin in different plants tissues, and the process by which the plant synthesizes suberin is important to improve plant growth and productivity under multiple environmental stresses and prevent spoilage of crops like potato in long-term storage. Chemically, suberin has two regions that differ in composition. One of the regions is composed of many aromatic compounds linked to each other by stable ether and carbon-carbon bonds. This region is referred to as the poly(aromatic) domain of suberin. The other region is composed of mostly aliphatic, and some aromatic compounds linked to each other by ester bonds. This region is referred to as the poly(aliphatic) domain of suberin. Studies to understand the function of suberin have been done mostly on the poly(aliphatic) domain of suberin. For example, the function of members of the BAHD family of enzymes, is well known to be involved in the formation of the poly(aliphatic) domain. Since these enzymes link aromatic and aliphatic components together, they may also function in the linking of poly(aromatic) and poly(aliphatic) domain of suberin. The objective of this research was to get a deeper understanding of the function of the BAHD family genes in the biosynthesis of the phenolic domain of suberin.

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