At present, in the summer, cockroaches usher in the peak of breeding, frequently lurking in residents' homes, which is a headache. Cockroaches are commonly known as cockroach insects, known as the undead "small strong", and are more common in American cockroaches, German cockroaches and Australian cockroaches.
As a worldwide household pest, the German cockroach has amazing fertility and rapid population growth. Figuring out the molecular mystery of the courtship mating of German cockroaches will help to prevent and control them scientifically and effectively.
Professor Li Sheng.
Recently, The team of Professor Li Sheng of the Institute of Entomology and Technology of the College of Life Sciences of South China Normal University identified the most critical genes of the contact sex pheromone synthesis pathway of German cockroaches through in-depth research, and on this basis, systematically revealed the molecular mechanism of sex and age-specific sexual attraction, providing a new idea for the prevention and control strategy aimed at interfering with the matema mating of German cockroaches. The relevant research results were recently published in the international authoritative journal Nature Ecology & Evolution.
Uncovering the Molecular "Code" of Contact Pheromone Synthesis
Unlike the American cockroach, which can reproduce parthenogenetically, the German cockroach can only reproduce as parthenogenetic, and sexually mature females synthesize contact pheromones that stimulate males to courtship and induce sexual mating. Although pheromones of the German cockroach have been systematically identified as early as the 1990s, the key genes that control this synthetic pathway are still unknown.
Why are only females able to synthesize sexual pheromones and have stronger sexual attraction after sexual maturity? Sex and age specificity of sex pheromone synthesis, and what upstream signaling pathways are precisely regulated? These interesting questions have been obscured for nearly 30 years. Around these problems, Professor Li Sheng's team carried out systematic research.
The staff conducted experiments.
Previously, it was believed that the pigment cells under the skin of the abdomen of the German cockroach were the main places for the synthesis of contact pheromones. The team integrated behavioral, biochemical, molecular, genetic and biogenetic analysis methods to screen and identify the CYP4PC1, the most critical contact pheromone synthesis pathway of German cockroaches, and found that the gene was highly expressed in the antennae and wings of female adults, thus negating the previous view of "contact pheromone synthesis under the abdominal body wall".
The team used RNA interference (RNAi) to significantly reduce the content of the rate-limiting enzyme gene in the females, and the results showed that the males no longer showed courtship behavior in these females. After the introduction of females into the control group, the males still exhibited normal courtship behavior. "These results suggest that the rate-limiting enzyme gene is necessary for the maintenance of contact pheromone synthesis and sexual attractiveness in females, and it is highly likely to be involved in the hydroxylation of contact pheromone precursors." Li Sheng said.
Sexually mature female cockroaches are more "charming"
The team further found that the expression of the tachycase gene and the content of contact pheromones were influenced by sex differentiation genes and juvenile hormone (JH) signals, which made the females more sexually attractive after sexual maturity.
Li Sheng introduced that sex differentiation genes play a role in regulating the development and maintenance of sex characteristics, and juvenile hormones, as one of the two endogenous hormones of insects, not only inhibit the metamorphosis of nymphs, but also act as gonadotropins to promote adult reproduction. After the female feathers, the concentration and signal of sparing hormones rise with the process of sexual maturation.
Cockroaches raised.
Studies have shown that the hydroxylation step in the contact pheromone synthesis pathway is promoted by sparing young hormones. To further demonstrate that the rate-limiting enzyme gene controls this decisive hydroxylation step, the team then tested whether the gene was regulated by sparing hormone signaling. They treated females with exogenous sparing hormones that significantly induced rate-limiting enzyme gene expression; When the hormone signal is suppressed, the sexual attraction of females is weakened.
"The expression of the Tachystem gene is promoted by the biotropic hormonal signaling pathway, thereby maintaining a high sexual pheromone content in females after sexual maturity, stimulating courtship mating in males." Li Sheng explained.
The male cockroach's "femininity gene" is turned off
Male insects also have high levels of contact pheromone precursor compounds, why can't they synthesize sex pheromones? The team found that juvenile hormones can induce males to express the Tachymetha enzyme gene and synthesize contact pheromones, but the effect is very limited. "This suggests that there may be a more important factor that inhibits the expression of the rate-limiting enzyme gene in males." Li Sheng said.
Staff clean plastic storage boxes for cockroaches.
The study further found that the specific expression of tachycase genes in females was regulated by upstream sex differentiation signaling pathways. In German cockroaches, the intersex gene doublesex (dsx) produces different proteins dsxF and dsxM, respectively, in male and female adults. The male-specific product dsxM protein binds to the promoter of the rate-limiting enzyme gene, thereby inhibiting its transcription.
Li Sheng introduced that this shows that in male adults, dsxM protein inhibits the expression of rate-limiting enzyme genes, and males are relatively deficient in juvenile hormones, and the two together inhibit the synthesis of contact pheromones in males.
Cockroaches raised.
Cockroaches raised.
The sex differentiation gene dsxM plays a "brake" role in males, directly inhibiting the expression of the rate limiting enzyme gene; The intersex gene in the female worm is modified to spliced into dsxF protein, which can play a role in removing the "brake", and the juvenile hormone signal further plays an "accelerator" role in the female worm, promoting the high expression of the rate limiting enzyme gene in the sexual maturation process of the female worm, thereby mediating the sexual attraction of sex and age specificity.
"Why don't male cockroaches attract each other? Because its 'femininity gene' is turned off; why a sexually mature female cockroach is more attractive because of its high 'endocrine' levels. The team members vividly compared it.
[Reporter] Wang Xiangbo
【Shooting】Xu Hao
[Correspondent] Chen Nan Yang Liuqing
【Author】 Wang Xiangbo; Xu Hao
Guangdong education headlines