ER-derived bodies in root defence


Principal Investigator: A. Driouich

Participants: ML Follet-Gueye, M. Vicré-Gibouin


The endoplasmic reticulum (ER) body is a structure derived from the ER that assists the plant cell under various stress conditions. There have been indications that the ER bodies would be involved in defence of mechanically-stressed cotyledons and leaves of Arabidopsis, but not in the root cap or BLC (Matsushima et al., 2002). Our preliminary microscopic data (Driouich et al., unpublished, Fig. 2c-d) revealed the presence of such structures in Arabidopsis roots including BLC. The goal of this section of the project is to characterize ER bodies in BLC and to investigate their possible function in plant defence. In order to determine whether the production of ER bodies are induced by treatment with elicitors (flg22 and PGN), ER body structures per BLC will be quantified. The ER bodies in Arabidopsis seedlings accumulate PYK10 protein, a -glucosidase that bears the ER retention signal KDEL. We will use both Arabidopsis seedlings expressing GFP-PYK10 and anti-PYK10 antibodies to visualize ER bodies using confocal microscopy. Biochemical fractionation will be performed according to Matsushima et al. (2003) in order to isolate ER bodies and comparative proteomic studies will be carried out to identify proteins induced by elicitor/pathogen treatments. Furthermore, subcellular localization of elicitors and/or pathogen-induced proteins in ER bodies (and otherwise within the secretory system) will be undertaken using antibodies raised against defensive proteins (e.g. anti-chitinase, anti-glucanase…) in conjunction with cryofixation and immuno-gold electron microscopy. We also make the hypothesis that ER bodies would reach and fuse with the plasma membrane upon treatment with elicitors. This will be examined using TIRF (Total Internal Reflection Fluorescence) microscopy on isolated BLC expressing fluorescent ER bodies.