Juvenile hormone may be key in controlling cotton aphid

The transition from playback mode to Aphis gossypii, the cotton aphid, depends on the action of juvenile hormone (JH). This was the main discovery of a team of researchers from the Chinese Academy of Agricultural Sciences, who investigated the genetic regulation of a lesser phase of the species: the gynoparous — winged females that appear in the fall and give rise to the sexual lineage of the pest.

During autumn, the reduction in photoperiod induces the emergence of these winged females. They abandon the summer host and migrate to winter host plants, where they generate sexual offspring and complete the holocyclic heteroecious cycle -- predominant in more than 90% of aphid species.

Gynoparae fulfill a critical reproductive function: they bridge the gap between asexual reproduction in spring and summer and fertilization before winter.

The study documented the morphological development stages of gynoparae of A. gossypii, characterized by abdominal growth, progressive darkening of color, formation of wing primordia and waxy spots arranged in abdominal zones in a “U” shape.

Dissections showed that only one embryo per ovary completes development, resulting in a low average fecundity: 7,3 offspring per female.

Results of the study

To understand the underlying hormonal mechanisms, the researchers applied kinoprene—a synthetic analogue of JH—to newborn nymphs.

The result: 100% of the treated individuals presented abnormalities, such as atrophied or malformed wings, and almost complete loss of reproductive capacity. The higher the dose and the longer the exposure, the more severe the deformations.

Transcriptomic analyses revealed significant alterations in genes involved in the synthesis and degradation of juvenile hormone. The genes JHAMT (synthesis), JHE and JHDK (degradation) showed altered expression after kinoprene treatment. In cases of greater deformity, there was a strong activation of degradation genes and a sharp decrease in the expression of the synthesis gene. These findings suggest that the imbalance in JH homeostasis directly compromises both alar differentiation and ovarian maturation.

The study validated the hypothesis that wing morphogenesis and reproductive transition are coordinated by hormonal signaling, integrated into specific genetic networks.

The responses to kinoprene reinforce the complexity of this control: even brief, low-concentration exposures were sufficient to disrupt gynopara development.

Application in agriculture

From an agricultural perspective, the results open a new frontier for aphid management: hormonal blockade. The possibility of using compounds that mimic or inhibit JH in specific phases could interfere with the pest's reproductive continuity, especially during its seasonal transition.

Despite the progress, the authors warn of limitations. The correlation between gene expression and protein function still requires functional validation.

Future studies should employ techniques such as RNAi to silence key genes and confirm their phenotypic role. It will also be necessary to evaluate the effects of JH in strains from other regions and hosts.

More information can be found at doi.org/10.3390/insects16060559