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Contribution of oenocytes and pheromones to courtship behaviour in Drosophila.

Wicker-Thomas C, Guenachi I, Keita YF - BMC Biochem. (2009)

Bottom Line: Inactivation of desat1 in oenocytes resulted in a 96% and 78% decrease in unsaturated hydrocarbons in males and females, respectively.Female pheromones (dienes) showed a decrease of 90%.Knock-down results for desat1 suggest that there must be very little transport of unsaturated precursors from fat body to the oenocytes, so pheromone synthesis occurs almost entirely through the action of biosynthesis enzymes within the oenocytes.

View Article: PubMed Central - HTML - PubMed

Affiliation: CNRS, UPR9034, LEGS and University Paris Sud, 91198 Gif sur Yvette Cedex, France. Wicker@legs.cnrs-gif.fr

ABSTRACT

Background: In Drosophila, cuticular sex pheromones are long-chain unsaturated hydrocarbons synthesized from fatty acid precursors in epidermal cells called oenocytes. The species D. melanogaster shows sex pheromone dimorphism, with high levels of monoenes in males, and of dienes in females. Some biosynthesis enzymes are expressed both in fat body and oenocytes, rendering it difficult to estimate the exact role of oenocytes and of the transport of fatty acids from fat body to oenocytes in pheromone elaboration. To address this question, we RNAi silenced two main genes of the biosynthesis pathway, desat1 and desatF, in the oenocytes of D. melanogaster, without modifying their fat body expression.

Results: Inactivation of desat1 in oenocytes resulted in a 96% and 78% decrease in unsaturated hydrocarbons in males and females, respectively. Female pheromones (dienes) showed a decrease of 90%. Inactivation of desatF, which is female-specific and responsible for diene formation, resulted in a dramatic loss of pheromones (-98%) paralleled with a two-fold increase in monoenes. Courtship parameters (especially courtship latency) from wild-type males were more affected by desat1 knocked-down females (courtship latency increased by four fold) than by desatF knocked-down ones (+65% of courtship latency).The number of transcripts in oenocytes was estimated at 0.32 and 0.49 attomole/microg for desat1 in males and females, respectively, about half of the total transcripts in a fly. There were only 0.06 attomole/microg desatF transcripts in females, all located in the oenocytes.

Conclusion: Knock-down results for desat1 suggest that there must be very little transport of unsaturated precursors from fat body to the oenocytes, so pheromone synthesis occurs almost entirely through the action of biosynthesis enzymes within the oenocytes. Courtship experiments allow us to discuss the behavioral role of diene pheromones, which, under special conditions, could be replaced by monoenes in D. melanogaster. A possible explanation is given of how pheromones could have evolved in species such as D. simulans, which only synthesize monoenes.

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RNAi knock-down of desatF in oenocytes leads to a dramatic decrease in dienes counter-balanced by an increase in monoenes. A. Percentages of different classes of hydrocarbons (dienes, monoenes, saturated, female pheromones, male-type pheromones) B. Percentages of the specific hydrocarbons according to their class and their length. All the hydrocarbon differences between control (1407-GAL4/+) and desatF knocked-down lines (1407-GAL4/UAS-desatF RNAi) were significantly different (P < 0.001, Student's t-test).
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Figure 3: RNAi knock-down of desatF in oenocytes leads to a dramatic decrease in dienes counter-balanced by an increase in monoenes. A. Percentages of different classes of hydrocarbons (dienes, monoenes, saturated, female pheromones, male-type pheromones) B. Percentages of the specific hydrocarbons according to their class and their length. All the hydrocarbon differences between control (1407-GAL4/+) and desatF knocked-down lines (1407-GAL4/UAS-desatF RNAi) were significantly different (P < 0.001, Student's t-test).

Mentions: When 1407-GAL4 driver was used to target desat1RNAi, no lethality occurred and flies seemed unaffected in their behavior (locomotor activity). However, their hydrocarbon profiles were dramatically affected, with an almost complete disappearance of unsaturated hydrocarbons (-96% and -78% in males and females, respectively). The level of saturated linear hydrocarbons was multiplied by 4 in both sexes. In females, total dienes (and pheromones) were decreased by 90%, monoenes by 40%.


Contribution of oenocytes and pheromones to courtship behaviour in Drosophila.

Wicker-Thomas C, Guenachi I, Keita YF - BMC Biochem. (2009)

RNAi knock-down of desatF in oenocytes leads to a dramatic decrease in dienes counter-balanced by an increase in monoenes. A. Percentages of different classes of hydrocarbons (dienes, monoenes, saturated, female pheromones, male-type pheromones) B. Percentages of the specific hydrocarbons according to their class and their length. All the hydrocarbon differences between control (1407-GAL4/+) and desatF knocked-down lines (1407-GAL4/UAS-desatF RNAi) were significantly different (P < 0.001, Student's t-test).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2734525&req=5

Figure 3: RNAi knock-down of desatF in oenocytes leads to a dramatic decrease in dienes counter-balanced by an increase in monoenes. A. Percentages of different classes of hydrocarbons (dienes, monoenes, saturated, female pheromones, male-type pheromones) B. Percentages of the specific hydrocarbons according to their class and their length. All the hydrocarbon differences between control (1407-GAL4/+) and desatF knocked-down lines (1407-GAL4/UAS-desatF RNAi) were significantly different (P < 0.001, Student's t-test).
Mentions: When 1407-GAL4 driver was used to target desat1RNAi, no lethality occurred and flies seemed unaffected in their behavior (locomotor activity). However, their hydrocarbon profiles were dramatically affected, with an almost complete disappearance of unsaturated hydrocarbons (-96% and -78% in males and females, respectively). The level of saturated linear hydrocarbons was multiplied by 4 in both sexes. In females, total dienes (and pheromones) were decreased by 90%, monoenes by 40%.

Bottom Line: Inactivation of desat1 in oenocytes resulted in a 96% and 78% decrease in unsaturated hydrocarbons in males and females, respectively.Female pheromones (dienes) showed a decrease of 90%.Knock-down results for desat1 suggest that there must be very little transport of unsaturated precursors from fat body to the oenocytes, so pheromone synthesis occurs almost entirely through the action of biosynthesis enzymes within the oenocytes.

View Article: PubMed Central - HTML - PubMed

Affiliation: CNRS, UPR9034, LEGS and University Paris Sud, 91198 Gif sur Yvette Cedex, France. Wicker@legs.cnrs-gif.fr

ABSTRACT

Background: In Drosophila, cuticular sex pheromones are long-chain unsaturated hydrocarbons synthesized from fatty acid precursors in epidermal cells called oenocytes. The species D. melanogaster shows sex pheromone dimorphism, with high levels of monoenes in males, and of dienes in females. Some biosynthesis enzymes are expressed both in fat body and oenocytes, rendering it difficult to estimate the exact role of oenocytes and of the transport of fatty acids from fat body to oenocytes in pheromone elaboration. To address this question, we RNAi silenced two main genes of the biosynthesis pathway, desat1 and desatF, in the oenocytes of D. melanogaster, without modifying their fat body expression.

Results: Inactivation of desat1 in oenocytes resulted in a 96% and 78% decrease in unsaturated hydrocarbons in males and females, respectively. Female pheromones (dienes) showed a decrease of 90%. Inactivation of desatF, which is female-specific and responsible for diene formation, resulted in a dramatic loss of pheromones (-98%) paralleled with a two-fold increase in monoenes. Courtship parameters (especially courtship latency) from wild-type males were more affected by desat1 knocked-down females (courtship latency increased by four fold) than by desatF knocked-down ones (+65% of courtship latency).The number of transcripts in oenocytes was estimated at 0.32 and 0.49 attomole/microg for desat1 in males and females, respectively, about half of the total transcripts in a fly. There were only 0.06 attomole/microg desatF transcripts in females, all located in the oenocytes.

Conclusion: Knock-down results for desat1 suggest that there must be very little transport of unsaturated precursors from fat body to the oenocytes, so pheromone synthesis occurs almost entirely through the action of biosynthesis enzymes within the oenocytes. Courtship experiments allow us to discuss the behavioral role of diene pheromones, which, under special conditions, could be replaced by monoenes in D. melanogaster. A possible explanation is given of how pheromones could have evolved in species such as D. simulans, which only synthesize monoenes.

Show MeSH