The prospects of targeting messenger RNA surveillance factor PELOTA for developing virus resistance in plants

Figures

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  Fig. 1. PELOTA-HBS1 mediated degradation of aberrant mRNA through NGD pathway in mammals, yeast, and plants: A In mammals and yeasts, during translation, when prolonged ribosomal stalling occurs due to loop-like/secondary mRNA structures, the PELOTA-HBS1 complex recognizes stalled ribosomes. As a result, an endonuclease, which cleaves such mRNA, is recruited at the ribosome stalled site. Following the cleavage, ABCE1 is recruited, and along with PELOTA, it rescues the stalled ribosome. XRN1 exonucleases and the cytoplasmic SKI-exosome complex further degrade the cleaved mRNA fragments. B In plants, NGD is triggered exclusively when long A-stretches appear within the mRNA coding region. This activates an unidentified endonuclease that induces endonucleolytic cleavage at the ribosome stalled sites. After the mRNA cleavage, the PELOTA-HBS1 complex binds to the stalled ribosome. The HBS1 is probably released in the subsequent steps, allowing ABCE1 and PELOTA to rescue the stalled ribosome. Consequently, the resulting 5' and 3' cleaved mRNA fragments are further degraded by the SKI-exosome complex and XRN4, respectively. This diagram of the plant NGD pathway is inspired by the previous study…

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  Fig. 2. PELOTA-HBS1 mediated degradation of stop codon-less mRNA through NSD pathway in mammals, yeasts, and plants: A In mammals and yeast, ribosomal stalling due to stop codon-less mRNA is recognized by the PELOTA-HBS1 complex at the empty A site. HBS1 promotes the binding of PELOTA to the A-site of the 60 S subunit of the ribosome. An endonuclease is recruited, which cuts the mRNA at the stalled site. Following this, ABCE1 is recruited, and together with PELOTA it rescues the stalled ribosome. Further degradation of cleaved mRNA fragments occurs with XRN1 exonucleases and cytoplasmic exosomes. B The proposed NSD model for plants suggests that ribosome stalling takes place when it encounters the poly A tail of a nonstop mRNA. This leads to the recruitment of the PELOTA-HBS1 complex, which binds to the A-site of the stalled ribosome and facilitates the attachment of the SKI-Exosome complex. Consequently, the faulty mRNA is degraded by the SKI-Exosome complex, allowing the ribosome to be rescued by the PELOTA-HBS1 complex. This diagram of the plant NSD pathway is based on the model proposed by (Szádéczky-Kardoss et al. 2018a). This figure was created using Biorender.

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  Fig. 3. The role of PELOTA protein under susceptible and resistant conditions in Rice-SRBSDV-WBPH pathosystem: Under susceptible conditions, SRBSDV-encoded tubular protein P7-1 interacts with PELOTA protein in both rice and white-backed plant hopper, a key interaction required for the formation of viral replication complexes. However, knock-down and knock-out of Pelo expression in both WBPH and rice disrupted P7-1 tubule formation, thus inhibiting virus replication, and conferring resistance. This figure was created using Biorender.

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  Fig. 4. PELOTA-HBS1 mediated degradation of TuMV mRNA through NGD pathway: SCE1 mediated SUMOylation of PELOTA protein facilitates its interaction with the HBS1. This interaction is necessary for the PELOTA-HBS1 complex to identify the conserved G1−2A6−7 motif in the P3 cistron of TuMV and cause degradation of viral mRNA. This Figure was created using Biorender.

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  Fig. 5. Inhibition of PELOTA SUMOylation by TuMV NIb protein: TuMV NIb protein acts as a SUMOylation decoy, competing with the SCE1 for PELOTA SUMOylation. By reducing PELOTA SUMOylation, NIb disrupts the interaction between PELOTA protein and HBS1, and prevents the formation of PELOTA-HBS1 complex required to degrade viral mRNA. This figure was created using Biorender.