Plant NLRs: The Whistleblowers of Plant Immunity

Abstract

The study of plant diseases is almost as old as agriculture itself. Advancements in molecular biology have given us much more insight into the plant immune system and how it detects the many pathogens plants may encounter. Members of the primary family of plant resistance (R) proteins, NLRs, contain three distinct domains, and appear to use several different mechanisms to recognize pathogen effectors and trigger immunity. Understanding the molecular process of NLR recognition and activation has been greatly aided by advancements in structural studies, with ZAR1 recently becoming the first full-length NLR to be visualized. Genetic and biochemical analysis identified many critical components for NLR activation and homeostasis control. The increased study of helper NLRs has also provided insights into the downstream signaling pathways of NLRs. This review summarizes the progress in the last decades on plant NLR research, focusing on the mechanistic understanding that has been achieved.

Multiple Alleles Encoding Atypical NLRs with Unique Central Tandem Repeats in Rice Confer Resistance to Xanthomonas oryzae pv. oryzae

“…Most reported R genes encode nucleotide-binding domain and leucine-rich repeat containing proteins (NLRs) ( Mermigka et al., 2020 ), which are typically classified into two groups based on the structure of their N-terminal sequences. The TNL (TIR-NLR) group contains a Toll/interleukin receptor (TIR) domain, whereas the CNL (CC-NLR) group contains a coiled-coil (CC) motif ( van Wersch et al., 2020 ). The Arabidopsis genome has approximately 150 NLR-encoding genes, two-thirds of them encode TNLs and one-third encodes CNLs ( Meyers et al., 2003 ).…”

Precision Breeding Made Real with CRISPR: Illustration through Genetic Resistance to Pathogens

“…However, its development awaits a better molecular understanding of NLR function to precisely target the right motifs and will require special attention to preserve agronomic traits by avoiding improper regulation of NLRs that can result in autoimmunity. This highlights the need to find a balance between pathogen detection and fitness ( van Wersch et al., 2020 ).…”

“…While conventional resistance breeding can be very successful, it may be associated with linkage drag and the resistance conferred by single R genes may be rapidly bypassed by fast-evolving pathogens. Therefore, the precise engineering of R and S genes constitutes an exciting route for the development of genetically resistant crops ( Langner et al., 2018 ; Tamborski and Krasileva, 2020 ; van Wersch et al., 2020 ), thereby limiting the environmental impact of chemical control. Copying mutations across accessions can also circumvent linkage drags associated with classical breeding, as shown for other characters ( Li et al., 2017a ).…”

SCFSNIPER7 controls protein turnover of unfoldase CDC48A to promote plant immunity

“…One major NLR regulation mechanism is ubiquitin‐mediated proteasomal degradation (van Wersch et al ., 2020). Ubiquitination is a common mechanism for protein regulation in eukaryotes (Trujillo & Shirasu, 2010; Komander & Rape, 2012; Marino et al ., 2012).…”