Salicylic acid-mediated innate immunity in Arabidopsis is regulated by SIZ1 SUMO E3 ligase

Jiyoung Lee, Jaesung Nam, Hyeong Cheol Park, Gunm Na, Kenji Miura, Jing Bo Jin, Chan Yul Yoo, Dongwon Baek, Doh Hoon Kim, Jae Cheol Jeong, Donggiun Kim, Sang Yeol Lee, David E. Salt, Tesfaye Mengiste, Qingqiu Gong, Shisong Ma, Hans J. Bohnert, Sang-Soo Kwak, Ray A. Bressan, Paul M. HasegawaDae-Jin Yun

Research output: Contribution to journalArticlepeer-review

260 Citations (Scopus)


Reversible modifications of target proteins by small ubiquitin-like modifier (SUMO) proteins are involved in many cellular processes in yeast and animals. Yet little is known about the function of sumoylation in plants. Here, we show that the SIZ1 gene, which encodes an Arabidopsis SUMO E3 ligase, regulates innate immunity. Mutant siz1 plants exhibit constitutive systemic-acquired resistance (SAR) characterized by elevated accumulation of salicylic acid (SA), increased expression of pathogenesis-related (PR) genes, and increased resistance to the bacterial pathogen Pseudomonas syringae pv. tomato (Pst) DC3000. Transfer of the NahG gene to siz1 plants results in reversal of these phenotypes back to wild-type. Analyses of the double mutants, npr1 siz1, pad4 siz1 and ndr1 siz1 revealed that SIZ1 controls SA signalling. SIZ1 interacts epistatically with PAD4 to regulate PR expression and disease resistance. Consistent with these observations, siz1 plants exhibited enhanced resistance to Pst DC3000 expressing avrRps4, a bacterial avirulence determinant that responds to the EDS1/PAD4-dependent TIR-NBS-type R gene. In contrast, siz1 plants were not resistant to Pst DC3000 expressing avrRpm1, a bacterial avirulence determinant that responds to the NDR1-dependent CC-NBS-type R gene. Jasmonic acid (JA)-induced PDF1.2 expression and susceptibility to Botrytis cinerea were unaltered in siz1 plants. Taken together, these results demonstrate that SIZ1 is required for SA and PAD4-mediated R gene signalling, which in turn confers innate immunity in Arabidopsis.

Original languageEnglish
Pages (from-to)79-90
Number of pages12
JournalThe Plant Journal
Issue number1
Early online date6 Dec 2006
Publication statusPublished - Jan 2007


  • CC-NBS-type R gene
  • plant innate immunity
  • salicylic acid
  • SIZ1 SUMO E3 ligase
  • systemic-acquired resistance
  • TIR-NBS-type R gene
  • systemic acquired-resistance
  • plant-disease resistance
  • of-function mutations
  • PR gene-expression
  • cell-death
  • defense responses
  • PIAS proteins
  • signaling components
  • E3 ligase
  • activation


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