Suppression of the high LRO Nile red phenotype of <i>kat-1</i> by mutations in the proton coupled amino acid transmembrane transporter <i>skat-1</i>.

<p>(A) a <i>kat-1</i> mutant has a doubling of LRO Nile red. A <i>skat-1</i> single mutant has a 30% reduction in LRO Nile red. The <i>kat-1;skat-1</i> double mutant show a near complete absence of LRO Nile red, indicating that <i>skat-1</i> completely suppresses the high LRO Nile red of a <i>kat-1</i> mutant. Representative images of individual animals are shown in the right panel. (B) As with the <i>kat-1;skat-1</i> double mutant, loss of <i>skat-1</i> in mutants lacking serotonin (<i>tph-1</i> and <i>cat-4</i>) show a synergistic decrease in LRO Nile red. The dramatic increase in LRO Nile red in the <i>kat-1;tub-1</i> double mutant is strongly suppressed in the <i>kat-1;skat-1;tub-1</i> triple mutant (representative image shown at right). (A and B, N>25, significance by ANOVA with Bonferroni correction.) (C) <i>skat-1</i> acts in the intestine in a cell autonomous manner to regulate LRO Nile red. Expression of <i>skat-1</i> under the intestine specific promoter <i>vha-6</i> in a <i>kat-1;skat-1</i> double mutant fully restores the high LRO Nile red phenotype of a <i>kat-1</i> mutant, whereas expression in the nervous system under the <i>rab-3</i> promoter does not. (D) SKAT-1::GFP expressed under the intestine-specific vha-6 promoter highlights hollow vesicles which are also positive for autofluorescent material, likely representing lysosome-related organelles (<i>arrows</i>). A large amount of SKAT-1::GFP is localized to smaller, more punctate cytoplasmic structures and does not co-localize with autofluorescent material (<i>angle brackets</i>).