Wing polyphenism is an evolutionarily successful feature found in a wide range of insects. Long-winged morphs can fly, which allows them to escape adverse habitats and track changing resources, whereas short-winged morphs are flightless, but usually possess higher fecundity than the winged morphs. Studies on aphids, crickets, and planthoppers have revealed that the alternative wing morphs develop in response to various environmental cues, and that the response to these cues may be mediated by developmental hormones, although this work has yielded equivocal and conflicting results about exactly which hormones are involved. As it stands, the molecular mechanism underlying wing morph determination in insects has remained elusive.
They show that two insulin receptors, NlInR1 and NlInR2, play opposing roles in controlling long wing versus short wing development by regulating the activity of the forkhead transcription factor NlFOXO. NlInR1, acting via the phosphoinositol 3-kinase (NlPI3K)-protein kinase B (NlAkt) signaling cascade, leads to the long-wing morph if active and the short-winged morph if inactive. NlInR2, by contrast, functions as a negative regulator of the NlInR1-NlPI3K-NlAkt pathway: suppression of NlInR2 results in development of the long-winged morph. The brain-secreted ligand, NlILP3, triggers development of long-winged morphs. Their findings provide the first evidence of a molecular basis for the regulation of wing polyphenism in insects, and are also the first demonstration of a binary control over alternative developmental outcomes.
The results were published on Nature (DOI: 10.1038/nature14286) at 18:00 (Time Zone, London) on March 18, 2015. Dr. Xu Haijun is the first author and co-corresponding author. Xue Jian , a Ph. D candidate student, is the co-first author. Dr. Zhang Chuanxi is the co-corresponding author. This work was supported by National Basic Research Program of China (973 Program, no. 2010CB126205) and by the National Science Foundation of China (no. 31201509, and no. 31471765).
The migratory brown planthopper (BPH), Nilaparvata lugens (Hemiptera: Delphacidae), is the most serious insect pest of rice, a major food source for more than 50% of the world’s population. One evolutionary adaptation that is thought to be essential to the success of BPH is its striking wing dimorphism. Both female and male BPHs can develop into either a long-winged (LW) morph or a short-winged (SW) adult morph in response to environmental cues. Both morphs are morphologically indistinguishable during the nymphal stages. The capability to develop into the LW morph enables BPHs to migrate over long distances, resulting in extensive damage to rice production across wide geographic areas. Their work may provide a potential new strategy for planthopper control.
