|Zhu, Yu Cheng|
Submitted to: Journal of Insect Biochemistry and Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2001
Publication Date: 1/31/2002
Citation: ZHU, Y., MUTHUKRISHNAN, S., KRAMER, K.J. CDNA SEQUENCES AND MRNA LEVELS OF TWO HEXAMERIN STORAGE PROTEINS PINSP1 AND PINSP2 FROM THE INDIANMEAL MOTH, PLODIA INTERPUNCTELLA. JOURNAL OF INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 31:525-536. 2002. Interpretive Summary: The Indianmeal moth is an insect that attacks stored grain and cereal products causing extensive damage. In our studies of the normal development process of this insect, we have found that two proteins supply the essential amino acids needed by the insect as it matures from one life stage to another. Information on these two proteins will be useful in the development of new pest control methods. Techniques and compounds that inhibit the production or natural activities of these two proteins will stop the growth of this important pest insect.
Technical Abstract: In insects, storage proteins or hexamerins accumulate apparently to serve as amino acid sources during metamorphosis and reproduction. Two storage protein-like cDNAs obtained from a cDNA library prepared from fourth instar larvae of the Indianmeal moth (Plodia interpunctella) were sequenced. The first clone, PinSP1, contained 2431 nucleotides with a 2295 nucleotide open nreading frame encoding 765 amino acid residues. The second cDNA, PinSP2, consisted of 2336 nucleotides with a 2250-nucleotide open reading frame encoding 750 amino acid residues. PinSP1 and PinSP2 shared 59% nucleotide sequence identity and 44% deduced amino acid sequence identity. A 17-amino acid residue signal peptide and a molecular mass of 90.4 kDa were predicted for the PinSP1 protein, whereas a 15-amino acid residue signal peptide and a mass of 88 kDa were predicted for PinSP2. Both proteins contained conserved insect larval storage protein signature sequence patterns and were 60-70% identical to other lepidopteran larval storage proteins. Expression of mRNA for both larval storage proteins was determined using quantitative reverse transcription polymerase chain reaction. Only very low levels were present in the second instar, but both mRNAs dramatically increased during the third instar, peaked in the fourth instar, decreased dramatically late in the same instar and pupal stages, and were undetectable during the adult stage. Males and females exhibited similar mRNA expression levels for both storage proteins during the pupal and adult stages. The results support the hypothesis that P. interpunctella, a species that does not feed after the larval stage, accumulates these two storage proteins as reserves during larval development for subsequent use in the development of the pupal and adult stages.