2010 Annual Report 1a.Objectives (from AD-416) 1) Nematode CLE variable domain function, and. 2)nematode CLE processing activity in planta. 1b.Approach (from AD-416) Using agrobacterium-mediated transient expression systems to investigate nematode CLE processing in planta. 3.Progress Report The overall objective is to investigate the mechanisms of CLE peptide mimicry in plant-cyst nematode interactions. Cyst nematodes produce secreted effector proteins that function as peptide mimics of plant CLE signaling peptides hypothesized to play a role in modifying host root cells to form specialized feeding cells that support the growth of the parasite. The site of action and mechanism of delivery of CLE effectors to host plant cells by the nematode, however, have not been established. Using immunologic, genetic and biochemical approaches we revealed the localization and site of action of nematode-secreted CLE proteins in planta. We have also successfully established an in vivo assay to assess potential processing of nematode CLE proteins. Using an Agrobacterium-based transient expression system to express a targeted protein in tobacco leaf tissue, we have demonstrated processing of nematode CLE in planta. Using this approach, detailed studies can now be conducted to understand the mechanisms of nematode CLE peptide processing in planta and a potential role for host-specific processing of nematode CLEs. A further study of this CLE peptide mimicry will identify plant targets for generating transgenic crops with novel resistance to cyst nematodes. Progress is monitored through email and phone conversations.