Diapause Specific Expressed Sequence Tags of Antheraea mylitta Drury

Abstract

Daba bivoltine ecorace of tropical tasar silkworm Antheraea mylitta Drury undergoes facultative pupal diapause and shows different type of voltinism. During course of its long pupal diapause, erratic, unseasonal and unsynchronised emergence of adults is noticed and losses of seed stock range in between 10 - 30%. In order to avoid all these problems, proper understanding of induction, maintenance and termination state of diapause of this economically important insect is felt essential. The presence of diapause specific expressed sequence tags (ESTs) through PCR clones of Hsp70, Hsp23, hexamerins and PCNA genes have been reported in the present study. The ESTs obtained form the primers of Hexamerins were only seen when pupae were 65 and 165 days old. ESTSs obtained form the primers designed form Hsps 70 sequences were up regulated during early (D0), middle (D75) and late age (D135 to D165) of diapause period. The presence of Hsp23 was obtained during preparatory phase of diapause (IV instar) and pupae of early and mid aged diapause period (D0 to D75) and late age of diapause (D135 to D165). ESTs of Hsp22 were seen during preparatory phase of diapause (IV&V instar), throughout diapause period and even after diapause period was over. ESTs of Hsps90 were seen during preparatory stage (IV instar) and middle and late age of diapause period. Est of PCNA were down regulated throughout diapause period, their up regulation was seen at the time of diapause termination. Another group of ESTs obtained from different sets of Hsps 70 primers were up regulated intermittently through out the diapause period. Hsps90 were upregulated during middle and late age of true diapause period. At the fag end of true diapause period, ESTs disappeared when pupae became older than 165 days as no ESTs were seen when pupae were 195 days old indicating the actual age of diapause termination. It was also evidenced by the up regulation of PCNA.ESTs whose concentration remained very low through out the diapause period but its intensity increased at 195 days which further increased at 210 days. The pupae of Daba BV of 195 days and older can be further exploited for low temperature treatment to delay the moth emergence in adverse summer season so as to produce dfls matching with the actual cropping schedule.