The Coiled-Coil and Leucine-Rich Repeat Domain of the Potyvirus Resistance Protein Pvr4 Has a Distinct Role in Signaling and Pathogen Recognition

Abstract

The pepper Pvr4 protein encoding coiled-coil (CC) nucleotide-binding (NB) leucine-rich repeat (LRR) (NLR) confer hypersensitive response (HR) to potyviruses, including Pepper mottle virus (PepMoV), by recognizing the viral avirulence protein NIb. To figure out the Pvr4-mediated HR mechanism, we analyzed signaling component genes and structure-function relationships of Pvr4, using chimeras and deletion mutants in Nicotiana benthamiana. Molecular chaperone components including HSP90, SGT1, and RAR1 were required, while plant hormones and mitogen-activated protein kinase signaling components had little effect on Pvr4-NIb-mediated HR cell death. Domain swap analyses indicated that the LRR domain of Pvr4 determines recognition of PepMoV-NIb. Our deletion analysis further revealed that the CC domain or CC-NBARC domain alone can trigger autoactive cell death in N. benthamiana. However, the fragments having only an LRR domain could suppress CC-NBARC domain-induced cell death in trans. Further, C-terminal truncation analysis of Pvr4 revealed that a minimum three of five LRR exons showing high similarity was essential for Pvr4 function. The LRR domain may maintain Pvr4 in an inactive state in the absence of NIb. These results provide further insight into the structure and function of NLR protein signaling in plants.

The plant hypersensitive response: concepts, control and consequences

“…Silencing or mutation of any one of RAR1, SGT1 or HSP90 in many interactions is sufficient to abolish HR and to cause the reduction of NLR protein levels (e.g. Azevedo et al , ; Bieri et al , ; Hubert et al , ; Kim et al , ; Scofield et al , ). The role of SGT1 is not completely understood.…”

Extreme resistance toPotato Virus Yin potato carrying theRystogene is mediated by a TIR-NLR immune receptor

“…This clearly shows that Ry sto 's mode of action is EDS1-and NRG1-dependent ( Fig. 5), while Pvr-4 mediated ER to PVY infection in N. benthamiana is EDS1-independent (Kim et al 2018).…”

Genome-wide functional analysis of hot pepper immune receptors reveals an autonomous NLR cluster in seed plants

“…These genes are genetically linked 34 and oriented head-to-head so that they may share a promoter for simultaneous regulation of 35 transcription. Although in silico analyses revealed that NLRs with integrated domains are 36 common in higher plants, functional NLR pairs have been discovered in only a few plant 37 species (15). A more complex NLR model was reported as an 'NLR network', primarily in 38 Solanaceous plants.…”

“…Furthermore, the sequences of these 109 upstream NLR genes did not encode an integrated decoy domain, which is a typical feature of Although ROS production and upregulation of defense-related genes are typical immune 168 responses, we cannot exclude the possibility that they also occur as a consequence of cell 169 death. To verify that autoactive G10-NLR and G10-CC indeed trigger defense responses, we 170 performed a co-expression assay using a Potato virus X (PVX) vector encoding GFP (37). 171 We hypothesized that if autoactive G10-CC-or G10-NLR-mediated cell death is associated Recent studies revealed that NLR-mediated immunity involves a complex network and 267 many NLRs require helper NLRs to exert activity in the immune response (16,22).…”

“…In addition, among 22 Arabidopsis G10-CCs, 352 13 in N. benthamiana and 5 in lettuce have been shown to induce cell death (49). Third, a 353 functional analysis of known R genes reported that G10-NLRs specifically sense cognate 354 effector proteins (24,37). The CC domain of the functional G10-NLR RPS5 was shown to 355 play an important role in recognizing the cognate effector AvrPphB (24).…”