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. Author manuscript; available in PMC: 2019 Aug 6.
Published in final edited form as: Dev Cell. 2018 Jul 19;46(3):271–284.e5. doi: 10.1016/j.devcel.2018.06.017

Figure 7. Uncoupling the transcriptional and myosin-activating functions of Yki.

Figure 7

(A) Sequences of the first 34 amino acids of wild-type Yki and the YkiAcidA allele. Asterisks indicate acidic amino acids.

(B–E′) Mutation of acidic residues at the N-terminus of Yki blocks its ability to activate myosin. S2 cells expressing membrane-associated wild-type Myr-Yki (B–B‴) and Myr-YkiAcidA (C–C‴). Myr-YkiAcidA fails to activate Sqh. White arrows indicate transfected cells. Wing imaginal discs expressing Myr-YkiAcidA also fail to activate Sqh (D–E′). The two transgenes were integrated at the same landing site to ensure comparable expression levels.

(F–K) The myosin-activating function of Yki is required for proper growth. Homozygous ykiAcidA adults are smaller than controls (F). Representative images show that adult female wings from animals homozygous for the ykiAcidA allele are undergrown (G–H). Larval wing imaginal discs are similarly undergrown (I–K), with ykiAcidA/ykiB5 (ykiAcidA/−) animals displaying the strongest phenotype (the latter genotype does not survive to adults). Quantification of adult wing and larval wing disc sizes of the indicated genotypes confirms these differences (L–M). Data are represented as mean ± SEM. Asterisks represent statistical significance of the difference between selected groups (**** p<0.0001, One-way ANOVA and Tukey’s HSD test, n = number of wings [L]/wing discs [M]).

(N) Model of feedback regulation of the Hippo pathway. Two negative feedback mechanisms have been proposed in the regulation of the Hippo pathway (red circles). One is mediated through transcriptional upregulation of upstream components, including Mer and Ex, and the other is a consequence of morphogen-driven growth at the center of tissues and the resulting compression of those cells. We propose a positive feedback mechanism (green circle) in which cortical Yki at the AJR promotes myosin activation and increased tension via Strn-Mlck, which in turn further activates Yki by suppressing the Hippo pathway. See the Discussion for more details.

See also Figure S7.