Fig. 4
Hippo kinase signaling pathway controls muscle size. a Images of transverse sections of IFMs from young and aged (7- and 28-day-old) controls (Mhc-Gal4/+) and mutant flies with the muscle-specific Dg downregulation (Mhc>DgRNAi). Note the appearance of moderate muscle deterioration upon Dg downregulation in young flies (blue arrows) and strong muscle deterioration in aged flies (black arrows). b The bar graph shows the frequencies of moderate (blue bars) and strong (red bars) muscle degeneration in controls and in flies with Dg downregulation in the muscles. c Images of transverse sections of IFMs of aged mutant flies with kbr and yki up- or downregulation in the muscles. Note that in all genotypes, no obvious muscle degeneration is observed; however, the muscles appeared to be smaller in size. ***p ≤ 0.001; **p ≤ 0.01; *p ≤ 0.05. d Enlarged view of IFMs. Downregulation of Dg (Mhc-Gal4>DgRNAi) and up- and downregulation of yki (Mhc-Gal4 >ykiRNAi, Mhc-Gal4>yki) or kbr (Mhc-Gal4>kbrRNAi, Mhc-Gal4>kbr) result in the appearance of smaller muscles, when compared to control (Mhc-Gal4/+). The yellow dashed line outlines an individual muscle (muscle 5). Black arrows point to muscle atrophy, which is detected by smaller muscle cells clearly separated from the neighboring cells