The E3 Ubiquitin Ligase Activity of Arabidopsis PLANT U-BOX17 and Its Functional Tobacco Homolog ACRE276 Are Required for Cell Death and Defense

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Yang, Cheng-Wei ; González-Lamothe, Rocío ; Ewan, Richard A. ; Rowland, Owen ; Yoshioka, Hirofumi ; Shenton, Matt ; Ye, Heng ; O'Donnell, Elizabeth ; Jones, Jonathan D.G. ; Sadanandom, Ari (2006)
  • Publisher: American Society of Plant Biologists
  • Related identifiers: doi: 10.1105/tpc.105.039198
  • Subject: QH345 | Research Articles
    mesheuropmc: food and beverages | fungi

Previous analysis of transcriptional changes after elicitation of Cf-9 transgenic tobacco (<i>Nicotiana</i> <i>tabacum</i>) by Avr9 peptide revealed a rapidly upregulated gene, <i>ACRE276</i>. We show that <i>ACRE276</i> is transiently induced in wounded leaves within 15 min, but upon Avr9 elicitor treatment, this upregulation is enhanced and maintained until cell death onset in Cf-9 tobacco. <i>ACRE276</i> RNA interference (RNAi) silencing in tobacco results in loss of hypersensitive response (HR) specified by Cf resistance genes. <i>ACRE276</i> RNAi plants are also compromised for HR mediated by the tobacco mosaic virus defense elicitor <i>p50</i>. Silencing tomato (Lycopersicon esculentum) <i>ACRE276</i> leads to breakdown of <i>Cf-9</i>–specified resistance against <i>Cladosporium</i> <i>fulvum</i> leaf mold. We confirmed that tobacco <i>ACRE276</i> is an E3 ubiquitin ligase requiring an intact U-box domain. Bioinformatic analyses revealed <i>Arabidopsis</i> <i>thaliana</i> PLANT U-BOX17 (PUB17) and <i>Brassica</i> <i>napus</i> ARC1 as the closest homologs of tobacco <i>ACRE276</i>. Transiently expressing PUB17 in Cf-9 tobacco silenced for <i>ACRE276</i> restores HR, while mutant PUB17 lacking E3 ligase activity fails to do so, demonstrating that PUB17 ligase activity is crucial for defense signaling. <i>Arabidopsis</i> <i>PUB17</i> knockout plants are compromised in <i>RPM1-</i> and <i>RPS4</i>-mediated resistance against <i>Pseudomonas</i> <i>syringae</i> pv <i>tomato</i> containing avirulence genes <i>AvrB</i> and <i>AvrRPS4</i>, respectively. We identify a conserved class of U-box ARMADILLO repeat E3 ligases that are positive regulators of cell death and defense across the Solanaceae and Brassicaceae.
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