Multiple functional self-association interfaces in plant TIR domains

The self-association of Toll/interleukin-1 receptor/resistance protein (TIR) domains has been implicated in signaling in plant and animal immunity receptors. Structure-based studies identified different TIR-domain dimerization interfaces required for signaling of the plant nucleotide-binding oligomerization domain-like receptors (NLRs) L6 from flax and disease resistance protein RPS4 from Arabidopsis. Here we show that the crystal structure of the TIR domain from the Arabidopsis NLR suppressor of npr1-1, constitutive 1 (SNC1) contains both an L6-like interface involving helices alpha D and alpha E (DE interface) and an RPS4-like interface involving helices alpha A and alpha E (AE interface). Mutations in either the AE- or DE-interface region disrupt cell-death signaling activity of SNC1, L6, and RPS4 TIR domains and full-length L6 and RPS4. Self-association of L6 and RPS4 TIR domains is affected by mutations in either region, whereas only AE-interface mutations affect SNC1 TIR-domain self-association. We further show two similar interfaces in the crystal structure of the TIR domain from the Arabidopsis NLR recognition of Peronospora parasitica 1 (RPP1). These data demonstrate that both the AE and DE self-association interfaces are simultaneously required for self-association and cell-death signaling in diverse plant NLRs.11139Ysciescopu

Yeast viability during fermentation and sur lie ageing of a defined medium and subsequent growth of Oenococcus oeni

Copyright © 2008 Australian Society of Viticulture and Oenology Inc.Interactions between the yeast strain used for primary oenological fermentation and the bacterium used to conduct subsequent malolactic fermentation were studied under model winemaking conditions. A commercial Saccharomyces cerevisiae wine yeast (strains, EC 1118, AWRI 835 and CY-3079) was grown in a defined medium whose composition approximated grape juice. Fermentations by all strains reached dryness, and retained a cell viability of greater than 90% upon completion of fermentation. Highest total viable cell number and percentage of viable cells were recorded for EC 1118. A sur lie ageing of the fermented medium over a 12 week period revealed a bi-phasic decay of culture viability for all strains. Thus 99% of cells had died within 2 weeks post-fermentation. Viabilities were then stable for the subsequent 4-6 week period before a second decline phase ensued and ended in either a minimal (ca 100 CFU/mL, EC 1118) or no viable cells being detected at 12 weeks of ageing. The growth response of an Oenococcus oeni inoculum to yeast culture supernatants, previously aged for up to 12 weeks in the presence or absence of yeast lees, was evaluated in a bio-assay. In this way, yeast strains could be designated as being either inhibitory, neutral or stimulatory to the growth of O. oeni (strain Lc5p). Inhibition by supernatants of strain EC 1118 was evident, but found to be reduced by ageing the supernatant (with or without lees). Conversely, longer ageing on yeast lees increased the magnitude of the stimulatory response in O. oeni (strain Lc5p) to the supernatant from the wine yeast (strain CY-3079).Robert J. Patynowski, Vladimir Jiranek and Andrew J. Markide