High expression of PP2A-Aα is associated with diapause induction during the photoperiod-sensitive stage of the cotton bollworm, Helicoverpa armigera

Protein phosphatase 2A (PP2A) is a major serine-threonine protein phosphatase which regulates metabolism, transcription, RNA splicing, translation, differentiation, cell cycle, oncogenic transformation and signal transduction. PP2A-Aα, an isoform of PP2A-A, is a structural subunit of the PP2A complex. We identified the photoperiod-sensitive stage for pupal diapause induction to be from the fifth instar to the early sixth instar larvae in the cotton bollworm, Helicoverpa armigera. PP2A-Aα cDNA from brains of diapause-destined fifth instar larvae was obtained by suppressive subtractive hybridization using nondiapause-destined larval brains as a control. Developmental expression of PP2A-Aα mRNA during the photoperiod-sensitive stage was higher in brains of diapause-destined larvae, and the PP2A-Aα protein showed a similar expression pattern as the mRNA. When larvae were transferred from diapause-inducing short days to long days during the diapause-sensitive stage, both PP2A-Aα mRNA and protein decreased significantly, and diapause incidence was also reduced. Thus, high PP2A-Aα expression during the diapause-sensitive stage may play a crucial role in photoperiodic induction of diapause, suggesting that it may be a new player involved in the molecular mechanism for diapause induction.