Par-1 Regulates Tissue Growth by Influencing Hippo Phosphorylation Status and Hippo-Salvador Association
Figure 3
Inactivation of Par-1 reduces organ size and downregulates the Hpo pathway-responsive genes.
(A–B″) Inactivation of Par-1 restricts organ growth. Side view of adult fly eyes: wild-type (A) or eyes expressing Par-1 RNAi (A′) under the control of eyless-Gal4. Dorsal view of adult wings: wild type (B) or wings expressing Par-1 RNAi (B′) under the control of MS1096. The relative wing size was quantified using an unpaired t-test (B″). The results represented the mean ± SEM. *** means p<0.001 (n>6) for each genotype. (C–C′) Knockout of par-1 restricts cell growth. Drosophila third-instar larval eye discs containing par-1w3 clones were dissected. par-1 mutant clones were marked by the loss of GFP expression, while their twin spots were marked by increased GFP expression. The representative par-1 mutant clone and its twin spot were separately indicated by the white dashed line and red dashed line (C). The total area of the par-1 mutant clones or their twin spots within one eye disc were calculated (C′). The results represented the mean ± SEM. *** means p<0.001 (n>6) for each genotype. (D–D′) Par-1 knockdown initiates apoptosis. Drosophila third-instar larval control eye discs (D) or discs expressing Par-1 RNAi (D′) under the control of GMR-Gal4 were immunostained with a cleaved-caspase-3 antibody. Note that caspase-3 was cleaved to its active form when Par-1 RNAi was expressed. (E–H′) Par-1 knockdown suppresses the expression of the Hpo pathway-responsive genes. Wing discs expressing Par-1 RNAi with hh-Gal4 (E–E′, H–H′) or with act>CD2>Gal4 (F–F′) were immunostained to demonstrate the protein expression levels of EX-Z (E–E′), mic32-GFP (F–F′), and DIAP1 (G–H′). Cells expressing Par-1 RNAi were labeled either by the lack of Ci or CD2 expression. Note that the expression of EX-Z and DIAP1 was inhibited, whereas the levels of mic32-GFP were increased. The arrows indicate the P-compartment or clone regions. (I–J″) Loss of par-1 disrupts the expression of Hpo pathway-responsive genes. D. melanogaster third-instar larval eye discs containing par-1W3 clones were dissected and examined to determine the expression of diap1-lacZ (I–I″) and bantam-lacZ (J–J″). par-1 mutant clones were marked by the loss of GFP expression. Note the downregulation of diap1-lacZ and bantam-lacZ in the absence of Par-1. The clone regions are indicated by arrows.