Generation of canola lines with increased heat and drought tolerance by regulating phospholipid: diacylglycerol acyltransferase activity

Project Summary

Overview

Heat and drought stress can cause a severe negative impact on canola (mainly Brassica napus). Recent extreme heat waves and arid conditions in Western Canada have led to catastrophic yield losses of canola in some areas. Based on projections of global warming, these events are only likely to worsen in coming years, and without mitigation procedures crop losses will be inevitable.

The targeted identification of specific genetic determinants of stress adaptation and generation of related canola lines are effective approaches in breeding cultivars with strong stress resistance. Since canola’s value chain is centered largely on seed oil, it is attractive to simultaneously improve abiotic stress tolerance and increase/maintain seed yield and quality (oil content, fatty acid profile, etc.). Phospholipid: diacylglycerol acyltransferase (PDAT1) catalyzes a terminal step of seed oil formation, and recent studies indicate that PDAT1 over-expression can effectively increase heat tolerance in the model plant Arabidopsis. Since Arabidopsis and canola share very similar pathways in plant development and oil biosynthesis, and many genes have similar functions in both species, the elevated expression of canola PDAT1 (BnPDAT1) has the potential to increase canola’s heat and associated drought tolerance, while maintaining or even increasing seed yield and quality.

Based on preliminary data and canola materials generated, this project will evaluate canola lines with distinct modifications of BnPDAT1 under heat and drought stress. It will also identify additional candidate genes related to heat and drought stress in the context of BnPDAT1 via transcriptomic analysis. The resulting characterized canola lines and genes could then be used in the breeding of canola cultivars with improved heat and drought tolerance, as well as seed quality, to benefit canola producers and the canola industry in Canada.

Purpose

The project outcomes will be highly valuable for the canola industry to ensure sustainable crop productivity. The homozygous lines generated in this project could be directly used as breeding materials for gene pyramiding in canola. Moreover, the research team will also identify novel candidate genes related to heat and drought tolerance via a comprehensive evaluation of canola PDAT1 overexpression lines. These new candidate genes may work synergistically with PDAT1 in stress resilience, and thus their use as molecular markers for pyramiding may be an effective strategy to substantially enhance heat and drought tolerance.

The canola lines, genes and knowledge generated in the proposed project have the potential to lead to the development of valuable stress-tolerant canola cultivars through molecular-assisted breeding approaches, which will not only benefit public and private canola breeders, but will also benefit canola producers in Canada through the provision of resistant germplasms. In the long term, the successful completion of this project will also help improve canola production efficiency and improve the national and global competitiveness of the Canadian canola industry.

Objectives

The long-term objective is to diversify Canadian canola germplasm with stress resistance genes, to identify candidate genes involved in regulating heat and drought resistance, and to collaborate with canola breeders to develop tightly linked molecular markers (or markers from the gene itself) for these stress resistance genes through the application of traditional breeding and modern genomics tools. The characterization of lipid-related and other candidate genes, alone or in combination, for their functions in canola seed yield and quality, as well as resistance to heat and drought, are also important long-term objectives.

The overall objective is to evaluate canola lines with distinct modifications in BnPDAT1 under heat and drought stress during flowering, and to identify additional candidate genes related to heat and drought stress. The modified canola lines and the newly identified candidate genes, as well as the knowledge gained, could then be applied in canola breeding to improve canola stress response while maintaining/increasing seed yield and quality.

Specific objectives are to:

1. Generate homozygous BnPDAT1 overexpression canola lines from the heterozygous lines currently available in the lab.
2. Generate homozygous PDAT1 knock-out canola lines using CRISPR/Cas9 technology.
3. Evaluate responses to heat and drought stresses in canola lines generated in objectives 1&2.
4. Conduct transcriptomic analysis on resistant and susceptible lines to identify novel candidate genes that can be used in improving abiotic stress tolerance in canola.