Overexpression of Met or Gce in larval hemocytes is sufficient to increase lamellocyte formation in response to juvenile hormone mimic treatment

2020-04-20T22:13:20Z (GMT) by Areeba Choudhry
Ectopic juvenile hormone mimics (JHMs) have been known to induce melanotic pseudotumors in a juvenile hormone receptor (JHR), Methoprene-tolerant (Met), dependent way, for decades. This response resembles the tumor formation in hoptum-l mutants, with constitutively activated hop inducing a cellular immune response leading to the formation of lamellocytes. Lamellocytes are specialized hemocytes ordinarily only found in immune challenged larvae. Drosophila contain two JHRs, Met and gce. Previously, we found that two JHMs (methoprene and pyriproxyfen) induce lamellocyte formation in wildtype larvae and but fail to induce lamellocytes in Met-gce- larvae. Here we tested the hypothesis that overexpression of Met or gce in hemocytes would lead to increased lamellocyte formation in the presence of methoprene. We used the hemese-Gal4 driver to turn on UAS-Met or UAS-gce in hemocytes. A lethal phase analysis was conducted; there was no difference in eclosion rate between hemese-Gal4, hemese-Gal4>Met or hemese-Gal4>Gce animals. Lamellocyte induction was compared for each genotype treated with ethanol alone or 25 ug of methoprene in ethanol per vial. The results indicated that overexpression of the JH receptors are not enough for lamellocyte formation without methoprene as all of the ethanol treated larvae had zero lamellocyte induction. Overexpression of either Met or Gce was sufficient to increase lamellocyte production in response to methoprene. Mean lamellocyte count per larvae was estimated by counting 64 squares of a hemocyter. Mean lamellocyte count following treatment for Gal4>Met and Gal4>gce were both greater than Gal4 alone, (p=0.0003, p<0.0001), respectively. These results are consistent with the mutant results showing that lack of JHR leads to a lack of response, indicating that the lamellocyte induction is caused by the methoprene exposure. We hypothesize that the fat body also plays a role in this response. The next steps include conducting experiments to study the overexpression of UAS-Met or UAS-gce using Gal4 in the fat body.