Cloning and expression of the nuclear transcription factor SIβFTZ-F1 cDNA from Spodoptera fitura

Insect molting and metamorphosis are regulated by 20-hydroxyecdysone, which activates the ecdysone receptors, followed by expression of a series of transcription factors. Beta Fushi Tarazu-Factor 1 （βFTZ-F1） is one of these ecdysis-related earlyexpressed transcription factors. A βFTZ-F1 complementary DNA （cDNA） was cloned from Spodoptera litura. The full-length cDNA was 2 194 bp in length and the open reading frame ofS1βFTZ-F1 cDNA consisted of 1 659 bp and encoded a 552-amino acid protein with a molecular mass of 61.4 kDa. Homology analysis revealed that S1βFTZ-F 1 protein shared high identities to its homologues from other species. The A/B domains and the D domains were diverse among the insectβFTZ-F 1 proteins, but DNA binding domains （C domain） and the ligand binding domains （E domain） were highly conserved. Northern blot analysis detected a transcript of 2.2 kb in the epidermis of fifth to sixth molting larvae. Reverse transcription polymerase chain reaction revealed that SIβFTZ-F1 gene started to increasingly and periodically express before each molt, followed by a decrease during the intermolt stages.

Alternative splicing of POUM2 regulates embryonic cuticular formation and tanning in Bombyx mori

Insect cuticle is an apical extracellular matrix produced by the epidermis,tracheal,hind-and foregut epithelia during embryogenesis and renewed during molting and metamorphosis.However,the underlying regulatory mechanism for embryonic cuticle formation remains largely unclear.Here,we investigate the function of the transcription factor POUM2 in the embryonic cuticular formation in Bombyx mori,a model lepidopteran insect.Clustered regularly interspaced palindromic repeats(CRISPR)/CRISPR-associated protein-9-mediated knockout of POUM2 resulted in the defect of cuticular deposition,pigmentation,and sclerotization in the embryos.Differentially expressed transcripts analysis of 7-d-old embryos identified 174 up-or downregulated cuticular protein transcripts,8 upregulated chitin degradation transcripts,2 downregulated chitin synthesis transcripts and 48 up-or downregulated transcription factor transcripts in the POUM2−/−embryos.The expression levels of the key factors of the tyrosine metabolic pathway,such as tyrosine hydroxylase(Th),Dopa decarboxylase(DDC),and arylalkylamine N-acetyltransferase(aaNAT),were significantly decreased in the POUM2−/−embryos.POUM2 isoform POUM2-L specifically bound the POU cis-regulatory element(CRE)in the Th promoter and increased the transcription of Th,whereas POUM2-S could not bind the POU CRE,although it also increased the transcription of Th.Heterogeneous nuclear ribonucleoprotein Squid-1 directly bound the POUM2 pre-mRNA(messenger RNA)and inhibited the alternative splicing of POUM2-L to POUM2-S mRNA.These results suggest that POUM2 participates in the cuticular formation by regulating the chitin and cuticular protein synthesis and metabolism,and the cuticular pigmentation and sclerotization by regulating tyrosine metabolism during embryogenesis.This study provides new insights into novel function of POUM2 in embryogenesis.