Heat-mediated manipulation of gene expression by IR-LEGO in the developing genitalia in <i>Drosophila</i>

Manipulating gene expression in a tissue-specific and temporally controlled manner is essential for understanding the function of the focal genes. Still, in many cases, the limited availability of specific promotors to drive ectopic manipulation remains a restricting factor in developing organs, even in Drosophila. Developing external genitalia is one such organ with a complex anatomical structure shaped by a joint regulatory network of many transcription factors. To overcome the restriction, we employed the infrared laser-evoked gene operator system (IR-LEGO), in which infrared laser (1,480 nm) irradiation induces gene expression under the control of a heat shock promoter. Pupal genital structures were irradiated at approximately 24 or 48 hours after puparium formation. We tested a range of laser power and depth to the target structure by a reporter assay using green fluorescent protein, which was induced under the control of the heat shock protein 70 promoter (hs-GAL4). In previous studies, the IR-LEGO has been used as a tool to induce ectopic transgene expression. In this study, we attempted to knock down genes such as yellow (y) and odd-paired (opa) ectopically by RNAi using the GAL4/UAS system. The results demonstrated that this technique has a high potential in manipulating transcript abundance levels in small groups of cells in specific genital structures to unravel novel functions of genes involved in the morphogenesis of species-specific and rapidly evolving anatomical structures.