Thesis Format
Monograph
Degree
Master of Science
Program
Biology
Supervisor
Bernards, Mark A.
2nd Supervisor
Dhaubhadel, Sangeeta.
Affiliation
London Research and Development Centre, Agriculture and Agri-Food Canada, 1391 Sandford St, London, Ontario, N5V 4T3, Canada
Co-Supervisor
Abstract
18-Hydroxyoleic acid and oleic-1,18-dioic acid are two of the most prominent aliphatic monomers in soybean root suberin. Previous study has demonstrated a positive correlation between CYP86A37 and CYP86A38 expression and the deposition of 18-hydroxyoleic acid in soybean hairy roots. By screening recombinant proteins through in vitro enzyme assays, the substrate specificities of CYP86A37, CYP86A38, and CYP86B9 – another suberin related CYP – were evaluated. Among the three recombinant enzymes, CYP86A38 was not expressed by yeast, whereas CYP86A37 and CYP86B9 exhibited a preference for the ω-hydroxylation of C18:1 and C24:0 fatty acids, respectively. Additionally, in vitro production of oleic-1,18-dioic acid was also detected when CYP86A37 was supplied with C18:1 FA substrate. In planta, CRISPR/Cas9-mediated double knockout of cyp86a37/cyp86a38 in soybeans resulted in significant reduction in most aliphatic suberin monomers, whereas overexpression of CYP86A38 did not result in an enhanced suberin phenotype. These findings underscore the role of the CYP86 subfamily in soybean aliphatic suberin biosynthesis.
Summary for Lay Audience
Soybean is the Canada’s third most valuable crop. However, its production is affected by root rot caused by a root pathogen. A possible method of managing root rot is to develop soybean cultivars with enhanced physical defence mechanisms. Suberin is a natural biopolymer that acts as a physical barrier to protect plants against water loss and pathogen infection. Soybean cultivars with more root suberin show greater resistance to root pathogens, making suberin a key focus in production of enhanced crops. My research aims to characterize key enzymatic steps involved in suberin biosynthesis. In soybeans, enzymes called cytochrome P450s (CYPs) are important enzymes for production of suberin. I tested the activities of three CYPs (CYP86A37, CYP86A38, CYP86B9). However, CYP86A38 did not show any activity under the experimental conditions that I tested it in. I found that CYP86A37 preferentially produced suberin monomers of 16 – 18 carbon chain length, while CYP86B9 preferred to produce suberin monomers with carbon chain length of 24. In plants, deleting CYP86A37, CYP86A38 from soybean also decreased suberin production. These results show that that CYPs are very important in suberin biosynthesis. This knowledge will lay the foundation towards developing more root rot resistant lines of soybean, protecting one of Canada’s most important crops.
Recommended Citation
Yeung, Lorena S., "Soybean Cytochrome P450s and The Making of Aliphatic Suberin Monomers" (2024). Electronic Thesis and Dissertation Repository. 10381.
https://ir.lib.uwo.ca/etd/10381
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