PREreviews of “The barley MLA13-AVRA13heterodimer reveals principles for immunoreceptor recognition of RNase-like powdery mildew effectors”

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The barley MLA13-AVR_A13heterodimer reveals principles for immunoreceptor recognition of RNase-like powdery mildew effectors

by Aaron W. Lawson, Andrea Flores-Ibarra, Yu Cao, Chunpeng An, Ulla Neumann, Monika Gunkel, Isabel M. L. Saur, Jijie Chai, Elmar Behrmann, and Paul Schulze-Lefert

Posted: July 17, 2024
Server: bioRxiv
DOI: 10.1101/2024.07.14.603419

Abstract

Co-evolution between cereals and pathogenic grass powdery mildew fungi is exemplified by sequence diversification of an allelic series of barley resistance genes encoding Mildew Locus A (MLA) nucleotide-binding leucine-rich repeat (NLR) immunoreceptors with a N-terminal coiled-coil domain (CNLs). Each immunoreceptor recognises a matching, strain-specific powdery mildew effector encoded by an avirulence gene (AVR_a₎. We present here the cryo-EM structure of barley MLA13 in complex with its cognate effector AVR_A13-1. The effector adopts an RNase-like fold when bound to MLA13in planta, similar to crystal structures of other RNase-like AVR_{A e}ffectors purified fromE. coli. AVR_A13-1 interactsviaits basal loops with MLA13 C-terminal leucine rich repeats (LRRs) and the central winged helix domain (WHD). Co-expression of structure-guided MLA13 and AVR_A13-1 substitution variants show that the receptor–effector interface plays an essential role in mediating immunity-associated plant cell death. Furthermore, by combining structural information from the MLA13–AVR_A13-1 heterocomplex with sequence alignments of other MLA receptors, we designed a single amino acid substitution in MLA7 that enables expanded effector detection of AVR_A13-1 and the virulent variant AVR_A13-V2. In contrast to the pentameric conformation of previously reported effector-activated CNL resistosomes, MLA13 was purified and resolved as a stable heterodimer from anin plantaexpression system. Our study suggests that the MLA13–AVR_A13-1 heterodimer might represent a CNL output distinct from CNL resistosomes and highlights opportunities for the development of designer gain-of-function NLRs.

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PREreview by Mauricio P. Contreras et al. of the TSL Preprint Club

Authored by Mauricio P. Contreras, AmirAli Toghani, Diana Gómez De La Cruz, Andrés Posbeyikian, and Josh Bennett of the TSL Preprint Club

Summary
This study explores the structural basis of pathogen recognition by the barley immune receptor MLA13 and its interaction with the effector protein AVR_A13-1 from the barley powdery mildew fungus Blumeria hordei.
Lawson et al. determined the structure of the MLA13 receptor bound to AVR_A13-1 at…

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PREreviews of The barley MLA13-AVRA13heterodimer reveals principles for immunoreceptor recognition of RNase-like powdery mildew effectors

1 PREreview

PREreviews of The barley MLA13-AVR_A13heterodimer reveals principles for immunoreceptor recognition of RNase-like powdery mildew effectors