SYNTHESIS OF THE SAME TWO PROTEINS PRIOR TO LARVAL DIAPAUSE AND PUPATION IN THE SPRUCE BUDWORM, CHORISTONEURA FUMIFERANA

Abstract Spruce budworm larvae produce large quantities of two proteins ( Choristoneura fumiferana diapause associated proteins 1 and 2, Cf DAP1 and Cf DAP2) that are diapause related. These proteins appeared soon after hatching and increased in abundance, reaching maximum levels by four days into the 1st instar, and they remained at high levels until three days after the termination of diapause. These two proteins were purified to homogeneity and their NH2-terminal sequences were obtained. Oligonucleotide primers designed on the basis of these NH2-terminal sequences were used in RT-PCR to isolate the cDNA fragments coding for these proteins. These PCR fragments were then used as probes to isolate the cDNAs that contained the complete coding region. The 2.5 kb mRNAs coding for these proteins started to appear 24 hr after hatching and large quantities of these mRNAs were detected in 1st instar and 2nd instar larvae until the 2nd instar larvae entered diapause. Low levels of these mRNAs were detected in the 2nd instar larvae that were preparing to enter diapause, in those that were in diapause as well as in those that terminated diapause. Low levels of Cf DAP1 mRNA were also detected on days 1 and 2 after ecdysis to the 3rd instar. However, no Cf DAP1 and Cf DAP2 mRNAs could be detected during the 4th and 5th instar larval stages. The mRNAs reappeared 24 hr after the 5th instar larvae molted into the 6th instar and increased to reach maximum levels by 60 hr after ecdysis. The mRNA levels remained high until 156 hr after ecdysis into the 6th instar (36–48 hr before pupal ecdysis), after which they disappeared once again. Immunocytochemical analyses showed that Cf DAP1 protein was present in 2nd and 6th instar larval fat body but not in 5th instar larval fat body. Thus, the same two genes were expressed for the first time before C. fumiferana larvae entered diapause and for a 2nd time before pupation.