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Abstract

Many plant pathogenic microbes secrete so-called effectors directly into the cytoplasm of host plants during infection, mainly to suppress host resistance mechanisms. In resistant cultivars, however, effectors can become recognized by immune receptors of the nucleotide-binding leucine-rich repeat (NLR) class, which surveille the host cytoplasm and may detect non-self or modified-self structures. Effector recognition and NLR activation entail a rapid immune response efficiently protecting the plant from microbial colonization, but processes downstream of receptor activation remain poorly understood. Plant NLRs are subdivided in two classes incorporating either a coiled coil (CC, CNLs) or Toll-Interleukin1-Receptor-like (TIR, TNLs) N-terminal domain. Analogous to animal NLRs, these N-terminal domains are considered to represent the signaling modules of plant NLRs. In agreement, TNLs, but not CNLs, functionally depend on the nucleo-cytoplasmic protein EDS1, qualifying EDS1 as a bona fide signaling component. From work in Arabidopsis, data will be presented how EDS1 may itself provoke clashes in the immune system and cause severe defense-over-growth trade-off. Furthermore, the establishment of Nicotiana benthamiana as a new model system for the analysis and functional dissection of EDS1-based heterodimers will be presented.