Developmental expression and hormonal regulation of male-specific Yellow Protein mRNA in adults of the desert locust , Schistocerca gregaria

Adult males of Schistocerca gregaria turn yellow when they become sexually mature. This is due to the deposition in the cuticle of a male-specific Yellow Protein (YP), of which the amino acid sequence is known. Yellowing only happens in crowd-reared (gregarious) males, and results from the deposition of a specific ‘Yellow Protein’. If individual males (solitarious) are isolated after the adult emergence, they become sexually mature but they do not turn yellow. On the basis of a partial YP-mRNA sequence, we established a reverse transcriptase polymerase chain reaction (RT-PCR) assay to study the developmental expression of YP in crowd-reared males, isolated-reared males and females. In crowd-reared adult males the transcription of YP gene started from day 5 on, and reached a maximum at day 12. The effects of juvenile hormone (JH), insulin (bovine), corazonin, ecdysone and 20 0H-ecdysone (20E) on the regulation of YP-mRNA synthesis were also investigated. JH made the cuticle turn yellow and, as shown by RT-PCR, YP-mRNA was induced. The effect of 100 μg JHIII was stronger than that of 10 μg. Insulin was only effective in inducing YP-mRNA synthesis at high dose (19 μg) and after more days (18 d). Corazonin and 20E made the cuticle turn black, but no YP-mRNA synthesis was observed. Ecdysone (10 and 100 μg) showed no effect on body coloration and YP-mRNA. Thus, JH was found to be the most potent inducer among the hormones tested.