Arabidopsis clathrin adaptor EPSIN1 but not MODIFIED TRANSPORT TO THE VACOULE1 contributes to effective plant immunity against pathogenic <i>Pseudomonas</i> bacteria

In eukaryotes, EPSINs are Epsin <i>N</i>-terminal Homology (ENTH) domain-containing proteins that serve as monomeric clathrin adaptors at the plasma membrane (PM) or the <i>trans-</i>Golgi Network (TGN)/early endosomes (EE). The model plant <i>Arabidopsis thaliana</i> encodes for seven ENTH proteins, of which so far, only <i>At</i>EPSIN1 (<i>At</i>EPS1) and MODIFIED TRANSPORT TO THE VACUOLE1 (<i>At</i>MTV1) localize to the TGN/EE and contribute to cargo trafficking to both the cell surface and the vacuole. However, relatively little is known about role(s) of any plant EPSIN in governing physiological responses. We have recently shown that <i>At</i>EPS1 is a positive modulator of plant immune signaling and pattern-triggered immunity against flagellated <i>Pseudomonas syringae</i> pv. <i>tomato</i> (<i>Pto</i>) DC3000 bacteria. In <i>eps1</i> mutants, impaired immune responses correlate with reduced accumulation of the receptor FLAGELLIN SENSING2 (<i>At</i>FLS2) and the convergent immune co-receptor BRASSINOSTEROID INSENTIVE1-ASSOCIATED RECEPTOR KINASE1 (<i>At</i>BAK1) in the PM. Here, we report that in contrast to <i>At</i>EPS1, the TGN/EE-localized <i>At</i>MTV1 did not contribute significantly to immunity against pathogenic <i>Pto</i> DC3000 bacteria. We also compared the amino acid sequences, peptide motif structures and <i>in silico</i> tertiary structures of the ENTH domains of <i>At</i>EPS1 and <i>At</i>MTV1 in more detail. We conclude that despite sharing the classical tertiary alpha helical ENTH-domain structure and clathrin-binding motifs, the overall low amino acid identity and differences in peptide motifs may explain their role(s) in trafficking of some of the same as well as distinct cargo components to their site of function, with the latter potentially contributing to differences in physiological responses.