ROLE OF CHILLING IN THE ACQUISITION OF COLD TOLERANCE AND THE CAPACITATION TO EXPRESS STRESS PROTEINS IN DIAPAUSING PHARATE LARVAE OF THE GYPSY-MOTH, LYMANTRIA-DISPAR

Cold hardiness in eggs (pharate first instar larvae) of the gypsy moth is not a component of the diapause program, but is acquired only after the pharate larvae have been chilled. The supercooling points of unchilled (25-degrees-C) and chilled (5-degrees-C) eggs are nearly the same (ca. -27-degrees-C), and chilling does not further elevate concentrations of glycerol, the major cryoprotectant, yet chilling at 5-degrees-C greatly increases the pharate larva's tolerance of -20-degrees-C. One conspicuous difference between the chilled and unchilled pharate larvae is their ability to express stress proteins. The most abundantly expressed stress protein, 75,000 M(r), was expressed more highly in chilled pharate larvae than in unchilled pharate larvae, both at high temperatures (> 40-degrees-C) and in response to low temperature (-15-degrees-C). This correlation suggests a link between stress protein synthesis and the acquisition of cold tolerance.