RPN1a, a 26S proteasome subunit, is required for innate immunity in Arabidopsis
Article first published online: 9 JUL 2012
© 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd
The Plant Journal
Volume 71, Issue 6, pages 1015–1028, September 2012
How to Cite
Yao, C., Wu, Y., Nie, H. and Tang, D. (2012), RPN1a, a 26S proteasome subunit, is required for innate immunity in Arabidopsis. The Plant Journal, 71: 1015–1028. doi: 10.1111/j.1365-313X.2012.05048.x
- Issue published online: 6 SEP 2012
- Article first published online: 9 JUL 2012
- Accepted manuscript online: 11 MAY 2012 12:43PM EST
- Received 1 December 2011; revised 4 May 2012; accepted 4 May 2012; published online 9 July 2012.
- powdery mildew;
- disease resistance;
- cell death;
Accumulating evidence shows that proper degradation of proteins that affect defense responses in a positive or negative manner is critical in plant immunity. However, the role of plant degradation systems such as the 26S proteasome in plant immunity is not well understood. Loss-of-function mutations in EDR2 (ENHANCED DISEASE RESISTANCE 2) lead to increased resistance to the adapted biotrophic powdery mildew pathogen Golovinomyces cichoracearum. To study the molecular interactions between powdery mildew pathogen and Arabidopsis, we performed a screen for suppressors of edr2 and found that mutation in the gene that encodes RPN1a, a subunit of the 26S proteasome, suppressed edr2-associated disease resistance phenotypes. In addition, RPN1a is required for edr1- and pmr4-mediated powdery mildew resistance and mildew-induced cell death. Furthermore, we show that rpn1a displayed enhanced susceptibility to the fungal pathogen G. cichoracearum and to virulent and avirulent bacterial Pto DC3000 strains, which indicated that rpn1a has defects in basal defense and resistance (R) protein-mediated defense. RPN1a–GFP localizes to both the nucleus and cytoplasm. Accumulation of RPN1a is affected by salicylic acid (SA) and the rpn1a mutant has defects in SA accumulation upon Pto DC3000 infection. Further analysis revealed that two other subunits of the 26S proteasome, RPT2a and RPN8a are also involved in edr2-mediated disease resistance. Based on these results, we conclude that RPN1a is required for basal defense and R protein-mediated defense. Our data provide evidence that some subunits of the 26S proteasome are involved in innate immunity in Arabidopsis.