Fig. 5. Reduced levels of Mlp84B result in a slower heart beat due to prolongation of the diastolic interval. (A) Heart period is significantly longer in 1 week old mlp84B^–/– flies compared with age-matched wild-type (wt) controls. Reintroduction of a mlp84B transgene in the mlp84B^–/– background results in partial rescue. (B) Heart-specific mlp84B knockdown prolongs the heart period in 5 week old flies compared with age-matched wild-type or UAS-mlp84B-RNAi outcrossed to wild-type flies. No significant increase in heart period was observed in 1 week old mlp84B RNAi-expressing flies. (C,D) Diastolic interval is significantly longer in 1 week old mlp84B^–/– and 5 week old mlp84B RNAi-expressing flies compared with corresponding controls (as in A and B). mlp84B^–/– rescue flies show intermediate diastolic interval duration (C). No significant prolongation of the diastolic interval was detected in mlp84B RNAi-expressing flies at 1 week of age (not shown). See supplementary material Fig. S1 for increases in standard deviations of the heart period and diastolic interval of 1 week old mlp84B^–/– flies and 5 week old mlp84B RNAi-expressing flies.