The complete cDNA sequences of heat shock protein 90 (hsp90) and of heat shock cognate protein 70 (hsc70) were cloned by reverse transcription polymerase chain reaction from the rice stem borer, Chilo suppressalis Walker. They potentially encode a 717-amino-acids (hsp90) and a 652-amino-acids (hsc70) protein, with calculated molecular weight of 82.5 and 71.3 kDa, respectively. The deduced amino acid sequence of hsp90 showed the highest homology of 97.2% to Spodoptera frugiperda hsp90. The closest match of C. suppressalis hsc70 was with Manduca sexta hsc70 at 98.0% identity. Expression of hsp90 in diapausing larvae was higher than that in non-diapausing larvae. No such up-regulation in diapausing larvae was observed for hsc70. In non-diapausing larvae, but not in diapausing ones, hsp90 expression was up-regulated by cold acclimation. Hsc70 expression slightly decreased during cold acclimation irrespective of the state of diapause. Involvement of hsp90 and hsc70 in larval diapause and cold tolerance acquisition in C. suppressalis is discussed.
Gene expressions of acclimatized and non-acclimatized diapausing larvae were examined in Chilo suppressalis using a subtraction technique. A gene encoding a methionine-rich storage protein, CsSP1, was cloned and its complete cDNA sequence was determined. Potentially, CsSP1 encoded a 758-amino acid protein, with a calculated molecular weight of 88.8 kDa. The expression level of CsSP1 was higher in nondiapausing larvae than in diapausing ones. The CsSP1 expression was up-regulated in diapausing larvae when the temperature of cold acclimation was shifted to 5 degrees C. The up-regulated level was maintained at 40 days after incubation at 5 degrees C. In nondiapausing larvae, CsSP1 expression was down-regulated when the temperature was below developmental zero. Involvement of CsSP1 in diapause, cold tolerance acquisition and postdiapause development in C. suppressalis is discussed.
The cDNA sequence of a small heat shock protein (hsp19.7) was cloned and sequenced from the rice stem borer, Chilo suppressalis Walker. The cDNA encoded a protein of 177 amino acids with a calculated molecular weight of 19.7 kDa. The deduced amino acid sequence showed the highest identity of 90% to Bombyx mori hsp19.9. Expression levels of hsp19.7 were similar between diapausing and non-diapausing larvae. In non-diapausing larvae, but not in diapausing ones, hsp19.7 expression was upregulated by cold acclimation. Involvement of hsp19.7 in larval diapause and cold tolerance in C. suppressalis is discussed.
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