<p>The ability of AX2 wild-type and of mutant slugs to migrate towards a light source (wavy line) was tested. While AX2 slugs (<b>top left image</b>) and AX2 slugs expressing p97-RFP (<b>bottom left image</b>) nicely migrated towards the light source, phototactic ability was severely impaired in the AX2/p97<sup>R115C</sup>-RFP strain (<b>middle left image</b>). In the ATG9<sup>KO</sup> strain phototaxis is completely lost (<b>top right image</b>). While expression of p97<sup>R155C</sup>-RFP in the ATG9<sup>KO</sup> strain partially rescued the phototactic ability (<b>middle right image</b>), no rescue of phototactic ability was observed upon expression of p97-RFP (<b>bottom right image</b>). The phototaxis assay was performed as described <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0046879#pone.0046879-Tung1" target="_blank">[28]</a>.</p
