Engineering nitrogen fixation
Workpackage I: N2 Fixation
During the Green Revolution nitrogen fertilisers as much as tripled cereal yields in some areas. However, these synthetic fertilisers remain unaffordable in developing countries, for example for smallholder farmers in sub-Saharan Africa whose yields are 15% to 20% of their potential. As part of the ENSA project (Engineering Nitrogen Symbiosis for Africa), Professor Giles Oldroyd’s group at the John Innes Centre is taking a synthetic biology approach to engineer nitrogen-fixation into cereals. The potential impact on yields in sub-Saharan Africa without reliance on chemical fertilisers is huge. Legumes are able to form symbiotic interactions with nitrogen-fixing rhizobial bacteria through formation of root nodules. Engineering this complex interaction into cereals is highly ambitious and could not be tackled without the tools of synthetic biology. Marchantia provides a fantastic platform for testing synthetic biology approaches in engineering symbiosis signalling that is directly linked to a strategic programme in cereals.
Simple systems for engineering symbiosis
OpenPlant supports an effort to establish Marchantia as a model system for signalling in symbiosis. Marchantia provides a potentially ground-breaking advance for testing and engineering symbiotic signalling. The Oldroyd and Schornack laboratories are exploring the domestication of new liverwort-fungi associations. New laboratory co-cultivation and marker techniques are being developed to study symbiotic interactions between Marchantia spp. and Glomermycota fungi. Access to simpler symbioses opens new approaches to engineering the precise signalling mechanisms that underpin mutualism.
Marchantia species and close relatives have been screened for their ability to form arbuscular mycorrhizal symbiosis. The Oldroyd lab has produced a draft of the 250Mb genome of Marchantia paleacea. In addition, high throughput methods have been developed for transformation of M. paleacea. We have developed techniques for routine production of Cas9-CRISPR-mediated knockout lines in different Marchantia species.
DNA parts and synthetic circuits
OpenPlant is supporting the assembly of a toolkit of standardised DNA parts for transcription factors and signalling components. These include LysM receptor-like kinases and novel cell reporters for high resolution cellular imaging. The DNA parts are compatible with the Phytobrick standard and Loop Assembly method. The toolkit will allow construction of new circuits for engineering synthetic responses to Nod factors, and rapid prototyping of synthetic circuits in transgenic Marchantia plants.
Conservation of signalling pathways in land-plants
The Schornack and Oldroyd labs recently demonstrated conservation of plant signalling pathways involved in plant interactions with pathogens (Carella et al., 2019) or fungal or bacterial endosymbionts (Radhakrishnan et al., 2020).
Carella et al., 2019, Figure 2: PR Protein Families Are Activated in Oomycete-Colonized M. polymorpha Thalli.
Marchantia liverworts display a dynamic molecular response to oomycete infection.
Features of conserved defenses are present in liverworts and angiosperms.
Distantly related plants activate phenylpropanoid metabolism during infection.
MpMyb14 regulates oomycete-induced biochemical defenses in liverworts.
“Plant diversification has led to the emergence of a tremendous diversity of mutualistic symbioses with microorganisms, ranging from extracellular associations to the most intimate intracellular associations, where fungal or bacterial symbionts are hosted inside plant cells.”
“Through analysis of 271 transcriptomes and 116 plant genomes spanning the entire land-plant diversity, we demonstrate that a common symbiosis signalling pathway co-evolved with intracellular endosymbioses, from the ancestral arbuscular mycorrhiza to the more recent ericoid and orchid mycorrhizae in angiosperms and ericoid-like associations of bryophytes.”
“This work unifies intracellular symbioses, revealing conservation in their evolution across 450 million yr of plant diversification.”
Publications
Radhakrishnan GV, Keller J, Rich MK, Vernié T, Mbadinga DLM, Vigneron N, Cottret L, Clemente HS, Libourel C, Cheema J, Linde AM, Eklund DM, Cheng S, Wong GKS, Lagercrantz U, Li FW, Oldroyd GED & Delaux PM. (2020) An ancestral signalling pathway is conserved in intracellular symbioses-forming plant lineages. Nature Plants 6: 280–289 https://doi.org/10.1038/s41477-020-0613-7 (Previously published on BioRxiv: https://www.biorxiv.org/content/10.1101/804591v1.full)
Carella P, Gogleva A, Hoey DJ, Bridgen AJ, Stolze SC, Nakagami H, Schornack S. (2019) Conserved Biochemical Defenses Underpin Host Responses to Oomycete Infection in an Early-Divergent Land Plant Lineage. Current Biology 29(14): 2282-2294.e5 https://doi.org/10.1016/j.cub.2019.05.078
Carella P, Evangelisti E, Schornack S (2018). Sticking to it: phytopathogen effector molecules may converge on evolutionarily conserved host targets in green plants. Curr Opin Plant Biol. 44:175-180. doi: 10.1016/j.pbi.2018.04.019.
Carella P, Gogleva A, Tomaselli M, Alfs C, Schornack S (2018). Phytophthora palmivora establishes tissue-specific intracellular infection structures in the earliest divergent land plant lineage. Proc Natl Acad Sci U S A. 115(16):E3846-E3855. doi: 10.1073/pnas.1717900115.
Carella P, Schornack S (2017). Manipulation of Bryophyte Hosts by Pathogenic and Symbiotic Microbes. Plant Cell Physiol. 59(4):651-660. doi: 10.1093/pcp/pcx182.
Delaux PM, Radhakrishnan G, and Oldroyd G (2015). Tracing the evolutionary path to nitrogen-fixing crops. Curr Opin Plant Biol. 26:95-9. doi: 10.1016/j.pbi.2015.06.003.
Delaux PM, Radhakrishnan G, Jayaraman D, Cheema J, Malbreil M, Volkening J, Sekimoto H, Nishiyama T, Melkonian M, Pokorny L, Rothfels C, Sederoff H, Stevenson D, Surek B, Zhang Y, Sussman M, Dunand C, Morris R, Roux C, Wong G, Oldroyd G, Ane JM (2015). Algal ancestor of land plants was preadapted for symbiosis. Proc Natl Acad Sci U S A. 112(43):13390-5. doi: 10.1073/pnas.1515426112.