Molecular cloning, expression pattern and comparative analysis of chitinsynthase gene B in Spodoptera exigua

摘要

The chitin synthase (CHS) gene B (4781 bp) of Spodoptera exigua (SeCHSB) was cloned by reverse-transcription PCR (RT-PCR) and 3'/5' RACEfrom the midgut. SeCHSB contains an open reading frame of 4572 nucleotides, encoding a protein of 1523 amino acids with a predicted molecular massof approximately 174.6 kDa. Alignment of SeCHSB with class B CHSs of other insects showed a high degree of conservation in the putative catalyticdomain region. The structure of the SeCHSB gene was analyzed and was found to be the same as that of Manduca sexta CHSB (MsCHSB), including 23exons and 22 introns but without alternative exons. Southern blot analysis revealed that SeCHSB was a single copy gene and the presence of only twochitin synthase genes in S. exigua. Further investigation indicated that SeCHSB was specifically expressed in the midgut, and its transcript existedconstitutively in the midgut from the 3rd instar larval stage to prepupae and reached highest expression on the 1st day of the fifth instar larval stage. Thesedata suggest that SeCHSB is very important in midgut formation and development. Chitin synthase gene comparisons between different classes ofinsects using software tools revealed some interesting aspects of the similarity and divergence of the gene in the Class Insecta.