Ten years ago, a plant-specific endomembrane compartment – the EXPO (Exocyst-PositiveOrganelle) was described. Markers for the Golgi, early or late endosome do not colocalize with double membrane EXPO; it is not induced by starvation, does not co-localize with autophagosomes and does not fuse with the vacuole. Instead, it fuses with the plasma membrane, releasing a single membrane vesicle into the cell wall, comprising a putative new EXPO exocytotic pathway. Further studies of this pathway focused on EXO70E2 subunit of the Arabidopsis exocyst complex. However, over the years we found that original EXPO features are mostly related to artefacts connected with exocyst subunits overexpression, and – most importantly - for the EXO70B1 isoform we proved unequivocally direct link to autophagy. In this project we will focus on major EXPO forming protein EXO70E2 and its closest homolog EXO70E1, test its direct connection to the autophagy pathway, address its currently unknown biological role, and clarify outstanding questions and problems of the EXPO compartment concept in plant cells.
Five relevant publications of the research group:
Kulich I, Pečenková T, Sekereš J, Smetana O, Fendrych M, Foissner I, Höftberger M, Žárský V. Arabidopsis exocyst subcomplex containing subunit EXO70B1 is involved in the autophagy-related transport to the vacuole. Traffic 14:1155-1165, 2013.
Pečenková T, Hála M, Kulich I, Kocourková D, Drdová E, Fendrych M, Toupalová H, Žárský V. The role for the exocyst complex subunits Exo70B2 and Exo70H1 in the plant-pathogen interaction. J Exp Bot.62:2107-16. 2011.
Sabol P, Kulich I, Žárský V. RIN4 recruits the exocyst subunit EXO70B1 to the plasma membrane. J. Exp. Bot. 68:3253-3265, 2017
Žárský V, Kulich I, Fendrych M, Pečenková T. Exocyst complex multiple functions in plant cells secretory pathways. Curr. Opinion Plant Biol. 16:726-733, 2013.
Žárský V, Sekereš J, Kubátová Z, Pečenková T, Cvrčková F. Three subfamilies of exocyst EXO70 family subunits in land plants: early divergence and ongoing functional specialization. J Exp Bot, 71:49-62, 2020.