Juvenile hormone titre and related gene expression during the change of reproductive modes in the pea aphid
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Most aphids show reproductive polyphenism, i.e. they alternate their reproductive modes from parthenogenesis to sexual reproduction in response to short photoperiods. Although juvenile hormone (JH) has been considered a likely candidate for regulating the transition from asexual to sexual reproduction after photoperiod sensing, there are few studies investigating the direct relationship between JH titers and the reproductive mode change. In addition, the sequencing of the pea aphid genome has allows identification of the genes involved in the JH pathway which then allows us to examine their expression levels in relation to the reproductive-mode switch. Using LC-MS in the pea aphid, JHIII titer was shown to be lower in aphids producing sexual morphs under short-days than in aphids producing parthenogenetic morphs in long-days. The expression levels of genes upstream and downstream of JH action were quantified by real-time qRT-PCR across the reproductive mode change. The expression level of JH esterase (JHE), which is responsible for JH degradation, was significantly higher in aphids reared under short-days. This suggests that the up-regulation of the JH degradation pathway may be responsible for the lower JHIII titer in aphids exposed to short-days, leading to the production of sexual morphs.
- Insect Molecular Biology
Insect Molecular Biology 21(1), 49-60, 2012-02