A Drosophila toolkit for HA-tagged proteins unveils a block in autophagy flux in the last instar larval fat body

The lysosomal function is down-regulated in the white prepupal fat body, resulting in the enlargement of lysosomes in the tissue. The enlargement is blocked by the forced activation of lysosomes by the overexpression of mitf, a sole homolog of the MiTF/TFE family transcription factors. Thus, it is possible to speculate that mitf participates in the down-regulation of lysosomes in the fat body. To test this possibility, we performed a comparative mRNA-seq of (1) wild-type white prepupal fat body, (2) mitf overexpressed white prepupal fat body, and (3) wild-type third instar larval fat body. First, a comparison of (1) and (2) showed that the overexpression of mitf upregulated transcription of most of the lysosome-related genes in the fat body, consistent with previous studies. Next, a comparison of (1) and (3) indicated that the transcription level of several lysosome-related genes was decreased in (1) compared to (3). However, most of the genes regulated by Mitf were not transcriptionally affected. These results suggest that mitf is dispensable for the downregulation of lysosomes in the white prepupal fat body. Overall design: Compare the effect of the overexpression of mitf at white prepupa. Or, compare the gene expression levels between third instar larvae and white prepupae in WT strain.