Abstract
In insects, juvenile hormone (JH) and 20-hydroxyecdysone (20E) regulate larval growth and molting. However, little is known about how this cooperative control is terminating larval diapause especially in the bamboo borer, Omphisa fuscidentalis. In both in vivo and in vitro experiments, we here measured the expression levels of genes which were affected by juvenile hormone analogue (JHA: S-methoprene) and 20-hydroxyecdysone (20E) in diapausing O. fuscidentalis larvae. Corresponding mRNA expression changes in the subesophageal ganglion (SG) and prothoracic gland (PG) were evaluated using qRT-PCR. The data showed similar response patterns of JH receptor gene (OfMet), diapause hormone gene (OfDH-PBAN), ecdysone receptor genes (OfEcR-A and OfEcR-B1) and ecdysone inducible genes (OfBr-C, OfE75A, OfE75B, OfE75C and OfHR3). JHA induced the expressions of OfMet and OfDH-PBAN in both SG and PG, whereas ecdysone receptor genes and ecdysone inducible genes were induced by JHA only in PG. For 20E treatment group, expressions of ecdysone receptor genes and ecdysone inducible genes in both SG and PG were increased by 20E injection. In addition, the in vitro experiments showed that OfMet and OfDH-PBAN were up-regulated by JHA alone, but ecdysone receptor genes and ecdysone inducible genes were up-regulated by JHA and 20E. However, OfMet and OfDH-PBAN in the SG was expressed faster than OfMet and OfDH-PBAN in the PG and the expression of ecdysone receptor genes and ecdysone inducible genes induced by JHA was much later than observed for 20E. These results indicate that JHA might stimulate the PG indirectly via factors (OfMet and OfDH-PBAN) in the SG, which might be a regulatory mechanism for larval diapause termination in O. fuscidentalis.
Highlights
Insect molting and metamorphosis are regulated by the interplay of two hormones, 20-hydroxyecdysone (20E) and juvenile hormone (JH) [1]
After the treatment of 0.5 μg juvenile hormone analogue (JHA), OfMet mRNA levels in the subesophageal ganglion (SG) were low on day 0, while levels of OfMet mRNA in the prothoracic gland (PG) were low until day 2
OfDH-PBAN mRNA levels in the SG were low from days 0 to 4, and gradually increased until reaching a maximum level on day 12, while OfDH-PBAN mRNA levels in the PG were low from days 0 to 8, and increased dramatically until reaching a peak on day 12 (ANOVA, P < 0.01)
Summary
Insect molting and metamorphosis are regulated by the interplay of two hormones, 20-hydroxyecdysone (20E) and juvenile hormone (JH) [1]. JH is generally synthesized by the corpora allata (CA), endocrine glands and contributes to the maintenance of larval growth. Larval diapause termination in Omphisa fuscidentalis and analysis, decision to publish, or preparation of the manuscript
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