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ARS Home » Midwest Area » St. Paul, Minnesota » Cereal Disease Lab » Research » Publications at this Location » Publication #421459
Research Project: Surveillance, Pathogen Biology, and Host Resistance of Cereal Rusts

Location: Cereal Disease Lab

Title: Putative neofunctionalization of a Poales-specific EXO70 clade

Author
item BERGUM, MOLLY - Sainsbury Laboratory
item SKLENAR, JAN - Sainsbury Laboratory
item HERNANDEZ-PINZON, INMACULADA - Sainsbury Laboratory
item TAYLOR, JODIE - Sainsbury Laboratory
item SMOKER, MATTHEW - Sainsbury Laboratory
item SAMWALD, SEBASTIAN - John Innes Center
item ALLEN, MEGAN - Sainsbury Laboratory
item THIND, ANUPRIYA - Sainsbury Laboratory
item GREEN, PHON - Sainsbury Laboratory
item MOON, HYERAN - University Of Minnesota
item MENKE, FRANKE - Sainsbury Laboratory
item ZIPFEL, CYRIL - University Of Zurich
item RHODES, JACK - Sainsbury Laboratory
item FAULKNER, CHRISTINE - John Innes Center
item Moscou, Matthew

Submitted to: bioRxiv
Publication Type: Pre-print Publication
Publication Acceptance Date: 12/17/2024
Publication Date: 12/17/2024
Citation: Bergum, M., Sklenar, J., Hernandez-Pinzon, I., Taylor, J., Smoker, M., Samwald, S., Allen, M., Thind, A., Green, P., Moon, H., Menke, F.L., Zipfel, C., Rhodes, J., Faulkner, C., Moscou, M.J. 2024. Putative neofunctionalization of a Poales-specific EXO70 clade. bioRxiv. https://doi.org/10.1101/2024.12.13.628418.
DOI: https://doi.org/10.1101/2024.12.13.628418

Interpretive Summary: Disease resistance in plants is primarily conferred by immune receptors that are located at the cell periphery or inside the cell. We previously identified the cell-surface immune receptor PUR1 that provides resistance to wheat stripe rust in barley and requires an EXO70 protein to facilitate the immune response. The EXO70 protein belongs to a group of proteins shared in animals, fungi, and plants, which has uniquely expanded in plants. While EXO70 proteins are known to be involved in secretion to the cell periphery, it was unknown whether the identified EXO70FX12 contributed to resistance by transporting defence compounds to the cell periphery or through another mechanism. In this work, we show that EXO70FX12 belongs to an expanded family of EXO70s only found in grasses and close grass relatives. Using a diversity of molecular techniques, we show that EXO70FX12 has lost its ability to participate in secretion indicating that this protein has gained a new, unknown function.

Technical Abstract: EXO70s are uniquely expanded in land plants compared to all other eukaryotic lineages. The functional implications of this expansion and diversification on the conserved role of EXO70 as a subunit of the octameric exocyst complex have remained unresolved. We previously demonstrated barley (Hordeum vulgare) EXO70FX12, a member of the monocot-specific EXO70FX clade, is required for resistance to wheat stripe rust in conjunction with the leucine-rich repeat receptor kinase (LRR-RK) HvPUR1. Through phylogenetic analysis, we identified unique features of the EXO70FX clade, leading us to hypothesize that this clade experienced neofunctionalization. Using structural predictions and protein-protein interaction assays, we demonstrate that HvEXO70FX12 lost the ability to serve as a subunit within the exocyst complex. We predict that the EXO70FX clade has largely lost exocyst association and represents a novel acquisition that emerged during Poales diversification for defence responses.