The C-terminal deletion mutants of HookA exhibit a defect in the HookA–early endosome interaction. (A) A diagram showing the wild-type HookA protein and the two C-terminal deletion mutants, ΔC-HookA and ΔC1-HookA, in which different amino acids are deleted. The red box indicates the putative microtubule-binding domain, the blue boxes indicate the three predicted coiled-coil domains, and the brown box indicates the C-terminal cargo-binding domain. (B) The ΔC-HookA and ΔC1-HookA mutants exhibit the same colony phenotype as that exhibited by the ΔhookA mutant. (C) The ΔC-HookA and ΔC1-HookA mutants show an obvious accumulation of mCherry-RabA–labeled early endosomes at the hyphal tip. The accumulation can be seen in ∼75% of the hyphal tips of both the ΔC-HookA and the ΔC1-HookA mutants (n = 98 for the ΔC-HookA mutant, and n = 102 for ΔC1-HookA mutant). See Video 3 for the phenotype of the ΔC-HookA mutant. (D) Kymographs showing an obvious accumulation of mCherry-RabA–labeled early endosomes at the hyphal tip in the ΔC-HookA and ΔhookA mutants and nonmotile early endosomes along the hyphae. (E) ΔC-HookA–GFP or ΔC1-HookA–GFP do not colocalize with the hyphal tip–accumulated early endosomes (100%, n = 50 for each mutant). (F) Western blots are shown to demonstrate that the ΔC-HookA–GFP or ΔC1-HookA–GFP proteins are expressed and stable. By measuring protein signal intensity on the Western blots in relation to protein loading as indicated by Ponceau S staining, we found that the level of ΔC-HookA–GFP relative to HookA-GFP is 1.17 ± 0.28 (mean ± SD; n = 3) and that of ΔC1-HookA–GFP relative to HookA-GFP is 0.99 ± 0.18 (mean ± SD; n = 3). There is no significant difference between the value of either mutant and that of the wild type at P = 0.05. Bars, 5 µm.