@phdthesis{Stegmann2013,
  author    = {Stegmann, Martin},
  title     = {Identification of PUB22 Targets and Functional Characterization in PAMP-Triggered Immunity},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-92061},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2013},
  abstract  = {The three closely related PUB proteins PUB22, PUB23 and PUB24 were described as important regulators for PTI signaling and plant immunity. To find cellular targets regulated by the action of the PUB triplet we performed a yeast two-hybrid screen to identify candidate target proteins of PUB22. We could identify Exo70B2 as a target protein of PUB22, which is ubiquitinated by the E3-ubiquitin ligase and consequently degraded in response to flg22 perception. The importance of Exo70B2 for immunity was shown by reverse genetics, demonstrating that exo70B2 mutants are impaired in PTI signaling and plant immunity. Exo70B2 is one of 23 homologs of the yeast Exo70p in Arabidopsis thaliana, which is a subunit of an octameric protein complex, termed the exocyst. The exocyst complex is required for the tethering of post-Golgi vesicles to specific target membranes and thus an important component of intracellular vesicle trafficking. The elucidated function of Exo70B2 and its requirement for PTI signaling is a novel finding and similar functions had not yet been described for the exocyst complex or subunits thereof in plants. Additional target proteins of PUB22 are also predicted to be involved in vesicle trafficking processes, suggesting that PUB22 has specialized to regulate trafficking protein complexes required for PTI signaling. Furthermore, the presented work suggests a mechanism for the regulation of Exo70B2 ubiquitination by PUB22. PUB22 was shown to be intrinsically instable due to its autocatalytic ubiquitination activity. Flg22 treatment induced the rapid post-translational stabilization of PUB22. This potentially enables the ligase to efficiently interact with Exo70B2, resulting in its polyubiquitination and 26S-proteasome-dependent turnover.},
  subject      = {Ubiquitinligase},
  language  = {en}
}