biostudies-literatureUnknown11(39)Pi QThe plant cysteine protease metacaspases are structural homologs of animal caspases and play pivotal roles under biotic and abiotic stresses. However, whether metacaspases and purine-rich element (R-motif)-mediated defense messenger RNA translation are involved in plant antiviral immunity remains elusive. Here, we report that barley stripe mosaic virus (BSMV) infection activates metacaspase 4 (MC4) to cleave the RNA binding protein lupus autoantigen 1 (La1) behind residue arginine-448. The cleaved La1_1-448 version relocates to the cytoplasm and promotes the R-motif-mediated cap-independent defense mRNA translation. Moreover, MC4 overexpression restricts BSMV infection in tobacco (<i>Nicotiana benthamiana</i>), whereas knockout of <i>MC4</i> and knockdown of <i>La1</i> are more sScience advanceseadv0819https://www.ebi.ac.uk/biostudies/studies/S-EPMC12459463biostudies-literatureThe MC4-La1 cleavage module restricts plant virus infection by integrating R-motif-mediated defense mRNA translation.PMC12459463Jiang ZLi DZhang YYang MChen YYue NWei JHu RSong WWang JPi QfalseThe MC4-La1 cleavage module restricts plant virus infection by integrating R-motif-mediated defense mRNA translation.The plant cysteine protease metacaspases are structural homologs of animal caspases and play pivotal roles under biotic and abiotic stresses. However, whether metacaspases and purine-rich element (R-motif)-mediated defense messenger RNA translation are involved in plant antiviral immunity remains elusive. Here, we report that barley stripe mosaic virus (BSMV) infection activates metacaspase 4 (MC4) to cleave the RNA binding protein lupus autoantigen 1 (La1) behind residue arginine-448. The cleaved La1_1-448 version relocates to the cytoplasm and promotes the R-motif-mediated cap-independent defense mRNA translation. Moreover, MC4 overexpression restricts BSMV infection in tobacco (<i>Nicotiana benthamiana</i>), whereas knockout of <i>MC4</i> and knockdown of <i>La1</i> are more s2025-01-01T00:00:00Z2025 Sep2026-06-03T19:49:56.34Z2026-05-01T03:10:44.862ZS-EPMC124594634099170710.1126/sciadv.adv0819