The clock gene, period, influences migratory flight and reproduction of the oriental armyworm, Mythimna separata (Walker)

Authors: JI, JIAYUE - CHINESE ACADEMY OF AGRICULTURAL SCIENCES; LIU, YUEQIU - CHINESE ACADEMY OF AGRICULTURAL SCIENCES; ZHANG, LEI - CHINESE ACADEMY OF AGRICULTURAL SCIENCES; CHENG, YUNXIA - CHINESE ACADEMY OF AGRICULTURAL SCIENCES; Stanley, David; JIANG, XINGFU - CHINESE ACADEMY OF AGRICULTURAL SCIENCES

Submitted to: Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2022
Publication Date: 10/28/2022
Citation: Ji, J., Liu, Y., Zhang, L., Cheng, Y., Stanley, D.W., Jiang, X. 2022. The clock gene, period, influences migratory flight and reproduction of the oriental armyworm, Mythimna separata (Walker). Insect Science. 30(3):650-660. https://doi.org/10.1111/1744-7917.13132.
DOI: https://doi.org/10.1111/1744-7917.13132

Interpretive Summary: The oriental armyworm is a major long-distance migratory insect pest of grain crops in China and other Asian countries. Virtually all organisms, from bacteria to mammals, operate under circadian rhythms, which helps them adapt to daily and seasonal changes that occur because of the Earth’s rotation around its axis and its annual rotations around the sun. The oriental armyworm migratory flights and reproductive behavior occur at night, regulated by a circadian rhythm. These rhythms are controlled by sets of genes called ‘clock genes’. In this paper we analyzed one of the clock genes and discovered that interrupting the gene led to disrupted nightly flight activity, mating and egg-laying. Disrupting these central features of oriental armyworm biology will block the ability of the pest insect to attack grain crops in many Asian countries. These clock genes represent new, specific targets that can be exploited to develop novel pest insect management technologies. Knowledge of these technologies will be used by scientists around the world to improve pest management. This will support global efforts to produce abundant safe and healthy foods for a rapidly growing human population.

Technical Abstract: The oriental armyworm, Mythimna separata is a major long-distance migratory insect pest of grain crops in China and other Asian countries. Migratory flights and reproductive behavior usually occur at night, regulated by a circadian rhythm. However, knowledge about the linkages between adult flight, reproduction and clock genes is still incomplete. To fill this important gap in our knowledge, a clock gene (designated Msper) was identified and phylogenetic analysis indicated that the encoded protein (MsPER) was highly similar to PER proteins from other insect species. qRT-PCR assays demonstrated significantly different spatiotemporal and circadian rhythmic accumulations of mRNA encoding Msper occurred during development under steady light-dark conditions of 14L:10D. The highest mRNA accumulation occurred in adult antennae and the lowest in larvae. Msper was expressed rhythmically in adult antennae, relatively lower in photophase and higher entering scotophase. Injecting siRNA into adult heads effectively knocked down Msper mRNA levels within 72 h. Most siRNA-injected adults reduced their evening flight activity significantly and did not exhibit normal evening peak of flight activity. They also failed to mate and lay eggs within 72 h. Adult mating behavior was restored to control levels by 72 h post injection. We infer that Msper is a prominent clock gene which acts in regulating adult migratory flight and mating behaviors of M. separata. Because of its influence on migration and mating, Msper may be a valuable gene to target for effective management of this migratory insect.