ABSTRACT
Met(27) is a null allele of the Methoprene-tolerant gene of D. melanogaster that shows resistance to the toxic effects of both juvenile hormone (JH) and a JH analog, methoprene. The mechanism of resistance appears to be altered JH reception. We measured fertility, JH-hydrolyzing activity, and dopamine (DA) levels in Met(27) and Met(+) flies under normal (25 degrees C) and heat-stress (38 degrees C) conditions. We show that under normal conditions Met(27) females have JH-hydrolyzing activity and fertility lower than Met(+), but DA content did not differ between the two strains. At 38 degrees C Met(27) flies show no impairment in JH-hydrolyzing activity in response to stress, but they do show lower DA levels and impaired reproduction. The results with Met(27) are consistent with the previous hypothesis that the alteration in fertility that follows heat stress in D. melanogaster could result from alteration in the JH endocrine system.
ABSTRACT
Activity levels of DOPA decarboxylase (DDC), an enzyme responsible for dopamine (DA) synthesis, and of N-acetyl transferase (NAT), an enzyme responsible for its degradation, were studied under normal and stress conditions in two lines of Drosophila virilis which are in contrast concerning their DA content under normal conditions and its alterations under stress. Interlinear differences in DDC activity were detected, and genetic analysis was carried out. It was found out that neither DDC nor NAT activity in D. virilis changed under stress. Based on the results of this study and data obtained earlier by the authors, a mechanism of DA content control under normal and stress conditions was proposed.
