A splicing variant of EDS1 from Vitis vinifera forms homodimers but no heterodimers with PAD4.

Enhanced Disease Susceptibility 1 (EDS1), a key component of microbe-triggered immunity (MTI) and effector-triggered immunity (ETI) in most higher plants, forms functional heterodimeric complexes with its homologs Phytoalexin-Deficient 4 (PAD4) or Senescence-Associated Gene 101 (SAG101). Here, the crystal structure of VvEDS1 Nterm , the N-terminal domain of EDS1 from Vitis vinifera, is reported, representing the first structure of an EDS1 entity beyond the model plant Arabidopsis thaliana. VvEDS1 Nterm has an α/β-hydrolase fold, is similar to the N-terminal domain of A. thaliana EDS1 and forms stable homodimers in solution as well as in crystals. These VvEDS1 Nterm homodimers are spatially incompatible with heterodimers with PAD4 or SAG101, they explain why VvEDS1 Nterm does not interact with Vitis vinifera PAD4 according to gel filtration, and they serve as a guide to develop a plausible, albeit experimentally not verified model of full-length VvEDS1. VvEDS1 Nterm is a splicing variant comprising two of three exons of the VvEDS1 gene. It originates from a naturally occurring mRNA, in which the first of two introns was removed while the second one containing a stop codon close to the exon/intron border was retained. This is a potential case of intron retention and the first report of this phenomenon in the context of EDS1. Its biological significance has not yet been clarified, nor has the question if a VvEDS1 Nterm protein with a specific function can occur under physiological conditions. This article is protected by copyright. All rights reserved.