Identification of novel serine proteinase gene transcripts in the midguts of two tropical insect pests, Scirpophaga incertulas (Wk.) and Helicoverpa armigera (Hb.).
We have used RT PCR and 3'RACE to identify diverse serine proteinase genes expressed in the midguts of the rice yellow stem borer (Scirpophaga incertulas) and Asian corn borer (Helicoverpa armigera). The RT-PCR primers encoded the conserved regions around the active site histidine57 and serine195 of Drosophila melanogaster alpha trypsin, including aspartate189 of the specificity pocket. These primers amplified three transcripts (SiP1-3) from midguts of S. incertulas, and two transcripts (HaP1-2) from midguts of H. armigera. The five RT PCR products were sequenced to permit design of gene-specific forward primers for use with anchored oligo dT primers in 3'RACE. Sequencing of the 3'RACE products indicated that SiP1, SiP2 and HaP1 encoded trypsin-like serine proteinases, while HaP2 encoded a chymotrypsin-like serine proteinases. The SiP3 transcript proved to be an abundant 960 nt mRNA encoding a trypsin-like protein in which the active site serine195 was replaced by aspartate. The possible functions of this unusual protein are discussed.
Mazumdar-Leighton
S
S
Department of Botany, Delhi University, India. sm90@nysaes.cornell.edu
Babu
C R
CR
Bennett
J
J
D000595:Amino Acid Sequence; D000818:Animals; D001224:Aspartic Acid / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics*; D004068:Digestive System Physiological Phenomena; D007915:Lepidoptera / Q000235:genetics*; D008969:Molecular Sequence Data; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012697:Serine Endopeptidases / Q000235:genetics*; D014357:Trypsin / Q000235:genetics
D017931:DNA Primers; D018076:DNA, Complementary; D001224:Aspartic Acid; D012697:Serine Endopeptidases; D014357:Trypsin