γ-glutamyl transpeptidase 1 specifically suppresses green-light avoidance via GABAA receptors in Drosophila.
Drosophila larvae innately show light avoidance behavior. Compared with robust blue-light avoidance, larvae exhibit relatively weaker green-light responses. In our previous screening for genes involved in larval light avoidance, compared with control w(1118) larvae, larvae with γ-glutamyl transpeptidase 1 (Ggt-1) knockdown or Ggt-1 mutation were found to exhibit higher percentage of green-light avoidance which was mediated by Rhodopsin6 (Rh6) photoreceptors. However, their responses to blue light did not change significantly. By adjusting the expression level of Ggt-1 in different tissues, we found that Ggt-1 in malpighian tubules was both necessary and sufficient for green-light avoidance. Our results showed that glutamate levels were lower in Ggt-1 null mutants compared with controls. Feeding Ggt-1 null mutants glutamate can normalize green-light avoidance, indicating that high glutamate concentrations suppressed larval green-light avoidance. However, rather than directly, glutamate affected green-light avoidance indirectly through GABA, the level of which was also lower in Ggt-1 mutants compared with controls. Mutants in glutamate decarboxylase 1, which encodes GABA synthase, and knockdown lines of the GABAA receptor, both exhibit elevated levels of green-light avoidance. Thus, our results elucidate the neurobiological mechanisms mediating green-light avoidance, which was inhibited in wild-type larvae.
State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China; University of the Chinese Academy of Sciences, Beijing, China.
Jiangqu
J
Liu
Zhefeng
Z
Gong
Li
L
Liu
D000818:Animals; D030801:Animals, Genetically Modified; D001362:Avoidance Learning / Q000187:drug effects*; D015153:Blotting, Western; D003116:Color; D004330:Drosophila; D055785:Gene Knockdown Techniques; D005968:Glutamate Decarboxylase / Q000235:genetics / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism / Q000502:physiology; D007814:Larva; D018377:Neurotransmitter Agents / Q000502:physiology; D010775:Photic Stimulation; D016133:Polymerase Chain Reaction; D034622:RNA Interference; D011963:Receptors, GABA-A / Q000187:drug effects* / Q000235:genetics; D005680:gamma-Aminobutyric Acid / Q000378:metabolism; D005723:gamma-Glutamyltransferase / Q000235:genetics* / Q000502:physiology*
D018377:Neurotransmitter Agents; D011963:Receptors, GABA-A; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D005723:gamma-Glutamyltransferase; D005968:Glutamate Decarboxylase
GABA; GABAA receptor; Ggt-1; Glutamate; green-light avoidance