Thesis Format

Integrated Article

Deciphering the Role of Cytochrome P450 Monooxygenases in Resistance to Phytophthora sojae in Soybean: Genomic Insight into Glyceollin Biosynthesis

Author

Praveen khatri, Western UniversityFollow

Degree

Doctor of Philosophy

Program

Biology

Supervisor

Dhaubhadel, Sangeeta

Affiliation

LONDON RESEARCH AND DEVELOPMENT CENTER

2nd Supervisor

Karagiannis, Jim

Co-Supervisor

Abstract

Root and stem rot, caused by the oomycete Phytophthora sojae, is a devastating disease in soybean that results in billions of dollars of annual losses worldwide. As a defence mechanism, soybean produces the phytoalexin glyceollin, which has demonstrated efficacy against multiple pathogens, including P. sojae. Interestingly, five steps in glyceollin biosynthesis are catalyzed by cytochrome P450 enzymes, highlighting the vital role of this class of enzymes in the defence against pathogen infection. My study thus aimed to identify and characterize the P450 genes (GmP450s) involved in glyceollin biosynthesis. Through bioinformatic analyses, I identified 346 GmP450s in the soybean genome. Using a multi-transcriptome and gene co-expression analysis strategies, 21 P450 candidates including members from the CYP73 and CYP81 families were selected for further study. The CYP73 family includes cinnamate 4 hydroxylase (C4H), which is the first P450 enzyme in the phenylpropanoid pathway (catalyzing the conversion of trans-cinnamic acid to p-coumaric acid). In this study, I identified four C4H genes in the soybean genome, three of which are functionally active. The CYP81 family, on the other hand, encompasses isoflavone hydroxylases (IFHs), which participate in the hydroxylation of isoflavone aglycons in legumes and, which initiate glyceollin production. The soybean genome contains 12 CYP81 candidates, nine of which are functional with diverse hydroxylation capabilities with soybean isoflavone aglycons. Catalytically efficient GmC4H and GmIFH enzymes have been identified and have great potential as molecular tools in metabolic engineering applications. Finally, a transcriptome study was undertaken to explore the differential temporal dynamics of GmP450s and glyceollin biosynthetic pathway genes in two soybean lines that differ in their resistance to P. sojae. The results suggest that the partially resistant line exhibits a stronger plant innate immunity compared to the susceptible cultivar. The study of P450s and the glyceollin biosynthesis pathway has provided new insights into their production and regulation and has highlighted the presence of important side branches in the isoflavonoid pathway in soybean.

Summary for Lay Audience

Soybean, an important crop worldwide, faces a major problem: a disease called root and stem rot. Caused by a type of microorganism named Phytophthora sojae, this disease leads to massive losses in soybean production, costing billions of dollars every year. Interestingly, soybeans naturally produce a substance called glyceollin that helps them fight off root and stem rot as well as other diseases. It is not fully understood how soybeans produce glyceollin. My research focused on uncovering specific genes that are part of a group called cytochrome P450 monooxygenases. This class of genes help plants create various essential substances, including the glyceollins. In my study, I looked at how soybean plants interact with the pathogen using several advanced genetic analysis methods. I found 21 genes that seem to play a role in how soybeans respond to the infection, including genes involved in the very first step of the process that eventually leads to glyceollin production. Understanding these genes is crucial because they can influence how well the plant can defend itself. Additionally, I studied how these P450 enzymes in soybeans help transform basic plant materials into glyceollin. To do this, I used a specialized technique to produce these enzymes in yeast, which allowed me to observe and measure their activity. Lastly, by comparing different types of soybean lines that vary in their resistance to the disease, I also shed light on the genetic response of soybeans to the disease over time. Some soybeans react quickly but briefly, while others respond more slowly and steadily. Ultimately, this research enhances our understanding of how soybeans produce protective substances like glyceollin. This knowledge opens up possibilities for improving soybean resistance to diseases through genetic engineering and could even allow us to produce these protective substances in other organisms, such as microbes, through biological engineering.

Recommended Citation

khatri, Praveen, "Deciphering the Role of Cytochrome P450 Monooxygenases in Resistance to Phytophthora sojae in Soybean: Genomic Insight into Glyceollin Biosynthesis" (2024). Electronic Thesis and Dissertation Repository. 10290.
https://ir.lib.uwo.ca/etd/10290

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