“Core” RxLR effectors in phytopathogenic oomycetes: A promising way to breeding for durable resistance in plants?

Abstract

Phytopathogenic oomycetes are known to successfully infect their hosts due to their ability to secrete effector proteins. Of interest to many researchers are effectors with the N-terminal RxLR motif (Arginine-any amino acid-Leucine-Arginine). Owing to advances in genome sequencing, we can now comprehend the high level of diversity among oomycete effectors, and similarly, their conservation within and among species referred to here as "core" RxLR effectors (CREs). Currently, there is a considerable number of CREs that have been identified in oomycetes. Functional characterization of these CREs propose their virulence role with the potential of targeting central cellular processes that are conserved across diverse plant species. We reason that effectors that are highly conserved and recognized by the host, could be harnessed in engineering plants for durable as well as broad-spectrum resistance.

Comparative Genome Analysis Across 128 Phytophthora Isolates Reveal Species-Specific Microsatellite Distribution and Localized Evolution of Compartmentalized Genomes

“…The standard effector prediction pipeline ( Chepsergon et al, 2021 ) was used to predict the effectors. The number of proteins retained in each step is shown in Supplementary Figure 6 .…”

Short Linear Motifs (SLiMs) in “Core” RxLR Effectors of Phytophthora parasitica var. nicotianae : a Case of PpRxLR1 Effector

“…These 71 core effectors probably have a more generalized and host-independent function, such as suppressing plant immunity ( 49 , 69 , 70 ). Since core effectors have the potential to target conserved plant proteins and processes ( 17 , 71 ), they can be harnessed in breeding for durable as well as broad-spectrum resistance in plants ( 43 , 72 ).…”

“…Although several conserved or “core” RxLR effectors (CRE) of oomycetes have been identified, only a few of these have been functionally characterized, hence making it difficult to have a consensus on the term CREs. In a recent review, CREs were defined as effectors that are conserved among strains of either a pathogen or different pathogen species, with the potential of playing a virulence role during infection process ( 43 ). These effectors are of importance since they are potential targets for breeding for durable resistance in plants ( 44 , 45 ).…”

The Minichromosome Maintenance Complex Component 2 (MjMCM2) of Meloidogyne javanica is a potential effector regulating the cell cycle in nematode-induced galls

“…This motif is implicated in translocation of the pathogen proteins into host cells 78 , 79 . Interestingly, signal peptide-lacking RxLR effector proteins have been shown to be secreted unconventionally 63 , 80 . In the past, there has been limited genetic information for PPNs, and initial scans of PPN genomes concluded that there were no effectors with RxLR or similar translocation motifs 81 , 82 .…”