The putative kinase substrate MUSE7 negatively impacts the accumulation of NLR proteins

Abstract

Stringent modulation of immune signaling in plants is necessary to enable a rapid response to pathogen attack without spurious defense activation. To identify genes involved in plant immunity, a forward genetic screen for enhancers of the autoimmune snc1 (suppressor of npr1, constitutive 1) mutant was conducted. The snc1 mutant contains a gain-of-function mutation in a gene encoding a NOD-like receptor (NLR) protein. The isolated muse7 (mutant, snc1-enhancing, 7) mutant was shown to confer a reversion to autoimmune phenotypes in the wild-type-like mos4 (modifier of snc1, 4) snc1 background. Positional cloning revealed that MUSE7 encodes an evolutionarily conserved putative kinase substrate of unknown function. The muse7 single mutants display enhanced resistance to the bacterial pathogen Pseudomonas syringae pv. tomato DC3000. While transcription of SNC1 is not enhanced, elevated SNC1 protein accumulation is associated with mutations in muse7. Accumulation of two additional NLR proteins, RPS2 (RESISTANCE TO PSEUDOMONAS SYRINGAE 2) and RPM1 (RESISTANCE TO PSEUDOMONAS SYRINGAE pv. MACULICOLA 1), was also observed in muse7 plants. Although proteasome-mediated degradation of NLR proteins is a well studied event in plant immunity, no interactions were detected between MUSE7 and selected components of this pathway. This study has demonstrated a role for MUSE7 in modulating plant immune responses through negatively affecting NLR accumulation, and will benefit future studies of MUSE7 homologs in other species.

Loss of the common immune coreceptor BAK1 leads to NLR-dependent cell death

“…S3 ). Since activated NLRs sometimes lead to the elevated transcriptional levels of their genes through a feedback loop, highly expressed NLR s might suggest the activation of the corresponding NLRs ( 30 ). We noticed three NLR subfamilies in which almost all their coding genes were highly up-regulated in bak1-4 bkk1-1 .…”

Plastic Transcriptomes Stabilize Immunity to Pathogen Diversity: The Jasmonic Acid and Salicylic Acid Networks within the Arabidopsis/Botrytis Pathosystem

“…In support of these observations was the finding that the top 100 correlated genes are enriched in biotic response terms when conducting a Gene Ontology (GO) enrichment analysis. At the other end of the spectrum, the gene with the highest negative correlation to lesion area was MUSE7, which is a conserved kinase substrate that influences NLR protein regulation (Johnson et al, 2017). The only enriched GO terms in the genes with a strong negative correlation to lesion size relate to photosynthesis.…”

Cell Death in Plant Immunity

“…Autoactive SNC1 has been shown to activate immune responses in the nucleus, where it represses small RNAs involved in NLR silencing (Cai et al 2018), and it associates with a transcriptional corepressor that blocks expression of negative regulators of immunity (Zhu et al 2010). To ensure appropriate activation of SNC1-dependent immunity, multiple repression mechanisms directed toward this protein have been shown at the transcriptional level as well as posttranscriptionally (Zhu et al 2010;Cheng et al 2011;Huang et al 2014;Johnson et al 2015Johnson et al , 2017Dong et al 2016;Gou et al 2017;Wang et al 2017aWang et al ,b, 2019cCai et al 2018;Zhang et al 2018;Niu et al 2019). The Rp1-D21 gene in maize, which derives from an intergenic recombination event between two NLR genes, Rp1-D and Rp1-dp2, provides another example of NLR autoactivation resulting in HR cell death (Chintamanani et al 2010).…”