Figure 3
Ykt6 is required for fusion of SGs with Lamp1+ but not Arl8+ vesicles, while Vamp7 is required for both. (a,c) In control larvae, maturing SGs fuse with Arl8+ lysosomes leading to the ring-like appearance of Arl8 around the Sgs3-dsRed+ SGs (turquoise arrowheads). Knockdown of ykt6 (b) does not affect these types of lysosomal fusions as Arl8 rings still appear around most SGs. (c,d) However, these fusions are inhibited in vamp7 silenced salivary glands (d) compared to the control (c), causing aggregation of the fusion incompetent Arl8+ lysosomes (yellow arrowheads) between the SGs (d). (e–h) Fusion of Lamp1+ vesicles supports the maturation of SGs and Lamp1 forms rings around SGs in control cells in a similar fashion to Arl8 (e). Ykt6 deficiency (f) strongly inhibits the fusion of SGs with Lamp1+ lysosomes/carrier vesicles, leading to the clustering of unfused dLamp1+ vesicles between SGs. (g,h) Silencing of vamp7 also inhibits these kinds of fusions, resulting in the accumulation of small-size Lamp1+ lysosomes around SGs that are unable to fuse (h), unlike in the corresponding control (g). (i–l) Quantification of the data shown in (a–h), n = 875 (a), n = 772 (b), n = 956 (c), n = 611 (d) Arl8+ structures and n = 513 (e), n = 724 (f), n = 516 (g), n = 1186 (h) Lamp1+ structures from 3 cells of 5 different larvae, ****p < 0.0001, ns p > 0.05. Insets show the outlined areas magnified (×2) and split into channels in panels (a–h).
