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Durham University

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Publication details for Professor Ari Sadanandom

Sadanandom, A. (2007). The U-box protein AtPUB17 is a functional ortholog of NtACRE276 and its E3 ubiquitin ligase activity is required for plant cell death and defence. Comparative Biochemistry And Physiology A-molecular & Integrative Physiology 146(4): S203-S203.

Author(s) from Durham


Previous analysis of transcriptional changes after elicitation of Cf-9-transgenic tobacco by Avr9 peptide revealed a rapidly upregulated gene NtACRE276. Here we show that NtACRE276 is transiently induced in leaves within 15 min by wounding, but upon Avr9 elicitor treatment this upregulation is further enhanced and maintained until the onset of cell death in Cf-9 tobacco. Silencing of NtACRE276 using RNAi in tobacco results in the loss of the hypersensitive response (HR) specified by Cf resistance genes. NtACRE276 RNAi plants are also compromised for HR mediated by the TMV defence elicitor, p50. Furthermore, silencing LeACRE276 in tomato leads to the breakdown of Cf-9-specified resistance against leaf mould caused by Cladosporium fulvum. We confirmed that NtACRE276 is an E3 ubiquitin ligase and that an intact U-box domain is required for this function. Bioinformatic analyses revealed that Arabidopsis PUB17 (AtPUB17) and Brassica napus ARC1 are the closest homologs of NtACRE276. Transiently expressing AtPUB17 in Cf-9 tobacco plants silenced for NtACRE276 leads to restoration of the HR whilst a mutant AtPUB17 lacking E3 ligase activity fails to do, demonstrating that the E3 ligase activity of AtPUB17 is crucial for defence signalling. AtPUB17 knockout plants are compromised in their RPM1- and RPS4-mediated resistance against Pseudomonas syringae pv. tomato containing avirulence genes AvrB and AvrRPS4, respectively. Our data identify the presence of a conserved class of U-box ARM repeat E3 ligases across the Solanaceous and Brassica genera that act as positive regulators of cell death and defence.