A reduction in ple protein levels, brought about through expression of one or two copies of ple^{dsRNA.Sym.Scer\UAS} under the control of Scer\GAL4^elav-C155, correlates with a reduction in larval feeding, despite the larvae appearing able to feed. While not significant, there is a trend towards increased branching of the 5-HT axonal fibers. However, the number and size of the 5-HT-containing vesicles are significantly increased with increasing knockdown of ple. Overall, the reduction in ple levels correlates with increased vesicle area. varicosity number is also increased. Exogenous dopamine exposure during the last 6 hours of embryogenesis can rescue the feeding behavior defects and fiber branching, total varicosity number, the number of varicosities greater than 5υm[2], and varicosity area found in Scer\GAL4^elav-C155 ple^{dsRNA.Sym.Scer\UAS}/ple^{dsRNA.Sym.Scer\UAS} mutants. There is no change in pupal size for these mutants and no change in time to pupariation, but there is a direct correlation between the extent of knockdown and the number of pupae.

Expression of ple^{dsRNA.Sym.Scer\UAS} in 2nd instar larvae, under the control of Scer\GAL4^{elav.Switch.PO} does not affect feeding behaviour, locomotion or gut fiber architecture. Branching, varicosity number, varicosity area and the number of large varicosities are unaffected.

Expression of ple^{dsRNA.Sym.Scer\UAS} in serotonergic neurons (under the control of Scer\GAL4^l.Trh.PK) does not affect feeding behaviour, while expression in DA neurons, under the control of Scer\GAL4^ple.PF) reduces feeding. Similarly, increased gut fiber branching and increased numbers of large 5-HT-containing vesicles are seen upon expression in DA neurons, but not upon expression in serotonergic neurons.