A lineage-specific Exo70 is required for receptor kinase-mediated immunity in barley

S. Holden; M. Bergum; P. Green; J. Bettgenhaeuser; I. Hernandez-Pinzon; A. Thind; S. J. Clare; J. M. Russell; A. Hubbard; J. Taylor; M. Smoker; M. Gardiner; L. Civolani; F. Cosenza; S. Rosignoli; R. Strugala; I. Molnar; H. Simkova; J. Dolezel; U. Schaffrath; M. Barrett; S. Salvi; M. J. Moscou

doi:10.1126/sciadv.abn7258

Plant BiologybioRxivDec 19, 2021

A lineage-specific Exo70 is required for receptor kinase-mediated immunity in barley

S. Holden, M. Bergum, P. Green, J. Bettgenhaeuser, I. Hernandez-Pinzon, A. Thind, S. J. Clare, J. M. Russell, A. Hubbard, J. Taylor, M. Smoker, M. Gardiner, L. Civolani, F. Cosenza, S. Rosignoli, R. Strugala, I. Molnar, H. Simkova, J. Dolezel, U. Schaffrath, M. Barrett, S. Salvi, M. J. Moscou

Abstract

In the evolution of land plants, the plant immune system has experienced expansion in immune receptor and signaling pathways. Lineage-specific expansions have been observed in diverse gene families that are potentially involved in immunity, but lack causal association. Here, we show that Rps8-mediated resistance in barley to the fungal pathogen Puccinia striiformis f. sp. tritici (wheat stripe rust) is conferred by a genetic module: LRR-RK and Exo70FX12, which are together necessary and sufficient. The Rps8 LRR-RK is the ortholog of rice extracellular immune receptor Xa21 and Exo70FX12 is a member of the Poales-specific Exo70FX clade. The Exo70FX clade emerged after the divergence of the Bromeliaceae and Poaceae, and comprises from 2 to 75 members in sequenced grasses. These results demonstrate the requirement of a lineage-specific Exo70FX12 in Rps8 LRR-RK immunity and suggest that the Exo70FX clade may have evolved a specialized role in receptor kinase signaling.

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