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Tomomi Nakagawa: How do host plants establish secure endo-symbioses with microbial partners?

  • Datum: 24.07.2017
  • Uhrzeit: 11:00 - 12:00
  • Vortragender: Tomomi Nakagawa
  • National Institute of Basic Biology/ Nagoya Univ.
  • Ort: MPIPZ
  • Raum: Lecture hall
  • Gastgeber: Kenichi Tsuda

Many terrestrial plants accept beneficial microbes inside their tissues, and also often inside the cell, and establish mutualistic symbioses. In most of these symbioses, host plants supply photosynthates in exchange for microbial duties such as a supply of nitrogen nutrients or phosphates. On the other hand, parasitic microbes also infect plant tissues and deprive the host of nutrients. To prevent an invasion of these pathogens, plants exploit multi-layered defense mechanisms, although rapidly-evolving pathogens often circumvent these and cause disease. My research interest is "How host plants accept beneficial microbial partners while rejecting pathogens". In this seminar, I will introduce our recent studies and discuss the two following topics: security against pathogenic accesses to host symbiotic systems, a host mechanism to prevent symbiont cheating in legume-rhizobia symbiosis. Plant receptor kinase, CERK1, is essential for the perception of fungal and bacterial cell wall components, chitin oligosaccharides and peptidoglycan, respectively, and triggers immune responses. In addition, pathogens often target CERK1 to circumvent host immunity by avirulence proteins. Thus, CERK1 plays key roles for plant security mechanisms. However, recently, we found that rice OsCERK1 regulates not only immune responses but also acceptance of beneficial arbuscular mycorrhizal (AM) fungi. The contrasting bifunctionality of CERK1 for both eliminating and accepting microbes seem to be common among terrestrial plants accepting AM fungi. I will discuss the potential meaning of this bifunctionality of CERK1. Legumes establish a mutualistic symbiosis with soil bacteria called rhizobia and develop nodules on roots. Inside the nodules, rhizobia fix atmospheric nitrogen to ammonia and supply it to the host plants in exchange for photosynthates. Host legumes recognize their symbiotic partners by Nod factors (NFs), symbiotic signal molecules secreted from rhizobia. However, NFs alone cannot guarantee the rhizobial nitrogen fixation because the genes involved in NF-synthesis or -secretion are independent from nitrogen fixation activity. How host legumes manage the risk of partner rhizobia cheating is largely unclear. I will discuss the host mechanism for this problem based on our recent findings

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