A downy mildew effector imposes host susceptibility by modulating the activity of a host RING E3 ligase required for immunity

KIM, DAE-SUNG; ASAI, SHUTA; FABRO, GEORGINA; FURLAN, GIULIA; TRUJILLO, MARCO; SKLENAR, JAN; MENKE, FRANK; FALTER-BRAUN, PASCAL; JONES, JONATHAN DG

Edimburgo

Simposio; From Proteome to Phenotype: role of post-translational modifications; 2017

Society for Experimental Biology

Pathogen effectors subvert host immunity by manipulating host physiology for the benefit of the pathogen. Hyaloperonospora arabidopsidis contains ~140 effector candidates carrying a signal peptide and an RxLR motif. HaRxL62 promotes plant susceptibility and is highly expressed during infection. Using IP-mass spec, we identified RING type E3 ligase (RING62) as an HaRxL62 interactor. RING62 is single copy in Arabidopsis, but well conserved in dicots as well as monocots. From previous studies, RING62 interacts in yeast two hybrid with RCD1, TCP14, TCP21, SAG102 and JAZ3. RING62 shows in vivo and in vitro auto-ubiquitination activity in an ATP-dependent manner. To reveal the effect of HaRxL62 on E3 ligase activity of RING62, we monitored E3 ligase activity after adding HaRxL62 in vitro as well as in vivo. E3 ligase activity seemed to increase in the presence of HaRxL62. However, RING62 self-association was not affected in the presence of HaRxL62. ring62 mutants show compromised resistance against Hpa and Pst DC3000. To reveal the regulatory network between HaRxL62 and RING62, we conducted yeast two hybrid screening using HaRxL62 or RING62 as a bait, respectively. TCP 3, 7, 9 and 15 interact with both HaRxL62 and RING62, whereas additional TCPs such as TCP 10, 13 and 23 were detected only in RING62 screening. Our goal is to elucidate how HaRxL62 elevates virulence by rendering RING62 hyperactive, so that HaRxL62 perturbs the balance of turnover and accumulation of its targets to suppress plant immune responses.