Juvenile hormone regulates photoperiod‐mediated male reproductive diapause via the methoprene‐tolerant gene in the ladybeetle Harmonia axyridis

Abstract

Juvenile hormone (JH) absence induces photoperiod-mediated reproductive diapause, which is characterized by reproductive cessation. Although the role of methoprene-tolerant (Met)-mediated JH signaling in photoperiod-mediated female reproduction has been well documented, its role in male reproduction remains unclear. In this study, we investigated the role of JH in regulating photoperiod-mediated development of the male internal reproductive system (IRS) in the predatory ladybeetle Harmonia axyridis (Pallas). In a previous study, we found that adult male H. axyridis reared under either a short-day (SD) or long-day (LD) photoperiod had obvious differences in IRS development, but we were unable to identify the regulators of male reproductive diapause. In this study, we found that beetles reared under an SD photoperiod had significantly lower JH titer and a relatively undeveloped male IRS compared with those reared under an LD photoperiod. Additionally, application of the JH analog (JHA) methoprene promoted IRS development. Furthermore, Met knockdown strongly blocked JH signaling in males reared under the LD photoperiod, thereby slowing IRS development. Moreover, exogenous JHA did not reverse the suppressed development of the male IRS caused by Met knockdown. These results indicate that photoperiod regulates male IRS development in H. axyridis through a conserved Met-dependent JH signaling pathway.

CYP314A1‐dependent 20‐hydroxyecdysone biosynthesis is involved in regulating the development of pupal diapause and energy metabolism in the Chinese citrus fruit fly, Bactrocera minax

“…[14][15][16][17][18][19][20] The reduction of JH titer triggers female reproductive diapause in Harmonia axyridis, 21 and JH regulates reproductive diapause via the methoprene-tolerant (Met) gene in male H. axyridis. 22 Similar results also have been found in female Colaphellus bowringi. 23 A 20E deficiency decreased ecdysis-triggering hormone signaling, reduced JH production, and induced diapause in C. bowringi.…”

“…Many previous studies have revealed that juvenile hormone (JH) and 20E signaling pathways participate in the regulation of diapause 14–20 . The reduction of JH titer triggers female reproductive diapause in Harmonia axyridis , 21 and JH regulates reproductive diapause via the methoprene‐tolerant (Met) gene in male H. axyridis 22 . Similar results also have been found in female Colaphellus bowringi 23 .…”

“…8), and 20E might be a key regulator of diapause development through its influence on energy storage and metabolism. Previous studies also have revealed that 20E can regulate energy accumulation for diapause preparation in both JH-dependent and -independent manners, 24 and JH signaling regulates the reproductive diapause of H. axyridis 22 and C. bowringi. 23 Moreover, insulin signaling in the fat body regulated by 20E has been documented in D. melanogaster 50 and B. mori, 51 and insulin signaling also regulates the overwintering diapause of Culex pipiens by influencing fat storage.…”

Temperature and metal ions regulate larval diapause termination via the 20‐hydroxyecdysone and juvenile hormone pathways in Monochamus alternatus

“…4 Disruption of diapause can be induced in several ways, including by environmental cues, chemicals and hormonal stimuli. [5][6][7][8] The termination of diapause is the least understood part of the diapause process, 9 although it is an indispensable step for postdiapause development, ultimately playing a vital role in insect survival. For diapausing larvae, the synchronization of diapause termination with the developmental season is critical to successful pupal metamorphosis.…”

“…Temperature and photoperiod were identified to induce facultative diapause in M. alternatus larvae 4 . Disruption of diapause can be induced in several ways, including by environmental cues, chemicals and hormonal stimuli 5–8 . The termination of diapause is the least understood part of the diapause process, 9 although it is an indispensable step for postdiapause development, ultimately playing a vital role in insect survival.…”