Re-Engineering of Mycorrhizal Symbiosis in Plants

Background

Arbuscular mycorrhizae (AM) are a symbiotic relationship in which soil fungi form nutrient exchange structures deep within the cells of their host plant’s roots. AM are one of the complex, but highly advantageous traits that can alleviate nutrient, water, and temperature stresses. However, the ability to form this symbiotic relationship was evolutionarily lost from economically important crops in the amaranth and brassica families, such as canola, sugar beets, cabbage, spinach, mustard greens, and many more. In addition to contributing nutrients, AM can also confer resistance to pests, pathogens, extreme temperatures, and soil toxins. This results in increased crop yield, but also increased resilience and resistance to climate change-driven stress. AM can be genetically engineered into non-mycorrhizal crops and modified in already mycorrhizal crops. Engineered AM further provide a strategy to manipulate other essential plant traits, including carbon storage, nitrogen fixation, and enhancement of the soil microbiome.

Technology Overview

Researchers at N.C. State University have discovered that a gene normally involved in arbuscular mycorrhizal (AM) symbiosis can alter transcription of a wide range of stress and biotic interaction related genes when used as a transgene in non-mycorrhizal crops. The gene, transcription factor Interacting Protein of DMI3 (IPD3), has been lost from non-mycorrhizal plants for millions of years and is subject to strong silencing in these species. Results have shown that the barriers to IPD3 transgenic expression can be overcome through rational gene and promoter modifications, allowing demonstration of its strong transcriptional effect on native genes. The ability of IPD3 to activate these molecular connections will be of interest for crop engineering applications in both pathogenic and symbiotic plant-microbe interactions, including direct engineering of AM and rhizobia.

These findings present an opportunity to increase the impact of AM via an engineered system designed to be more consistent and compatible with agricultural conditions. Such a system can contribute by improving performance of mycorrhizal symbiosis in existing host crops, expanding this beneficial symbiosis to new crop species, and, and making it easier for farmers to adopt the use of mycorrhizae as a biofertilizer in real-world agricultural conditions. Long-term impacts of engineered AM included reduced cost and environmental impact from synthetic fertilizers and pesticides, soil carbon storage, food stability and crop diversity.

Benefits

1. Interacting Protein of DMI3, a key transcription factor that enables AM within the common symbiosis pathway can be used as a transgene for crop engineering of non-mycorrhizal plants ().
2. Results have shown that an IPD3Min modified version under control of specific native regulatory sequences can escape silencing of this gene in non-mycorrhizal plants. This expands engineering possibilities to a large new category of crops.
3. Results have shown that IPD3Min once successfully expressed in nonmycorrhizal plants can be used to alter expression of native plant genes for multiple important traits beyond AM symbiosis. This includes pathogen immunity, flowering time, and environmental-stress-related genes.

Applications

Biological nitrogen fixation, soil microbiome, sustainable agriculture, and high yielding crops.

Publications

Hornstein ED et.al. Re-engineering a lost trait: IPD3, a master regulator of arbuscular mycorrhizal symbiosis, affects genes for immunity and metabolism of non-host Arabidopsis when restored long after its evolutionary loss. bioRxiv .2023 Mar 8:2023.03.06.531368.

Opportunity

Currently seeking collaborative and licensing opportunities.