A eukaryotic initiation factor 5C is upregulated during metamorphosis in the cotton bollworm, Helicoverpa armigera

A cDNA encoding a polypeptide of 419 amino acids containing an N-terminal leucine zipper motif and a C-terminal eIF5C domain was cloned from metamorphic larvae of Helicoverpa armigera. It was subsequently named Ha-eIF5C. Quantitative real-time PCR (QRT-PCR) revealed a high expression of the mRNA of Ha-eIF5C in the head-thorax, integument, midgut, and fat body during metamorphosis. Immunohistochemistry suggested that Ha-eIF5C was distributed into both the cytoplasm and the nucleus in the midgut, fat body and integument. Ha-eIF5C expression was upregulated by 20-hydroxyecdysone (20E). Furthermore, the transcription of Ha-eIF5C was down regulated after silencing of ecdysteroid receptor (EcR) or Ultraspiracle protein (USP) by RNAi.These results suggested that during metamorphosis of the cotton bollworm, Ha-eIF5C was upregulated by 20E through the EcR and USP transcription factors.To holometabolous insects, molting is a common physiological process, whose life cycles are characterized by a series of molts. During their larval molts, the larvae progress from one instar to the next. Thereafter, pupation and eclosion ensue during their metamorphic molts. Increasing evidence indicates that some hormones and receptors may contribute to the complex developmental pathways associated with molting and metamorphosis. Many genes have been shown to be involved in molting or metamorphosis, such as the transcription factors ecdysteroid receptor (EcR), Ultraspiracle protein (USP), Hormone receptor 3 (HR3) and Broad complex [1], and the programmed cell death pathway genes [2]. Some key regulatory genes have also been identified, such as E74B and E93 [3]. However, very few genes downstream of Broad complex, E74B and E93 have been identified. Consequently, there is a dearth of available knowledge on the molecular mechanisms that lead to larval molt and metamorphosis. By conducting a research of the molting related genes, we may further understand the molecular mechanism of development and