title: Old AIMs of the exocyst: evidence for an ancestral association of exocyst subunits with autophagy-associated Atg8 proteins.
abstract: In a recent addendum, Oren Tzfadia and Gad Galili (PSB 2014; 9:e26732) showed that several Arabidopsis exocyst subunits possess consensus Atg8-interacting motifs (AIMs), which may mediate their interaction with the autophagy-associated Atg8 protein, providing thus a mechanistic base for participation of exocyst (sub)complexes in autophagy. However, the bioinformatically identified AIMs are short peptide motifs that may occur by chance. We thus performed an exhaustive search in a large collection of plant exocyst-derived sequences from our previous bioinformatic study and found that AIMs are over-represented among exocyst subunits of all lineages examined, including moss and club moss, compared with a representative sample of the Arabidopsis proteome. This is consistent with the proposed exocyst AIMs being biologically meaningful and evolutionarily ancient. Moreover, among the numerous EXO70 paralogs, the monocot-specific EXO70F clade appears to be exempt from the general AIM enrichment, suggesting a modification of the autophagy connection in a subset of exocyst variants.
authors.affiliation: Department of Experimental Plant Biology; Faculty of Science; Charles University; Prague, Czech Republic.
authors.forename: Fatima
authors.initials: F
authors.lastname: Cvrčková
authors.affiliation: Department of Experimental Plant Biology; Faculty of Science; Charles University; Prague, Czech Republic.
authors.forename: Viktor
authors.initials: V
authors.lastname: Zárský
mesh_terms: D020816:Amino Acid Motifs; D017360:Arabidopsis / Q000166:cytology* / Q000378:metabolism*; D001343:Autophagy; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism*; D021122:Protein Subunits / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D021122:Protein Subunits
keywords: Atg8; EXO70; Physcomitrella; Selaginella; autophagy; dicots; evolution; exocyst; monocots; protein sequence patterns