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.

Keywords: :

• autophagy
• exocyst
• EXO70
• Atg8
• evolution
• protein sequence patterns
• monocots
• dicots
• Physcomitrella
• Selaginella

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Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

This work has been supported by the GACR P305/11/1629 grant from the Grant Agency of the Czech Republic and by the EU PLANTORIGINS-ITN 238640 project.