The segments 10 (S10) of the 11 double stranded RNA genomes from Antheraea mylitta cytoplasmic polyhedrosis virus (AmCPV) encoding a novel polyhedrin polypeptide was converted to cDNA. cloned, and sequenced. Three cDNA clones consisting of 1502 (AmCPV10-1), 1120 (AmCPV10-2), and 1415 (AmCPV10-3) nucleotides encoding polyhedrin of 254, 339, and 319 amino acids with molecular masses of 29, 39, and 37 kDa. respectively. were obtained. and verified by Northern analysis. These clones showed 70 94% sequence identity among them but none with any Sequences ill databases. The expression of AmCPV10-1 cDNA encoded polyhedrin in SO cells was detected by immunoblot analysis and formation of polyhedra by electron microscopy, as observed in AmCPV-infected gut cells. but no expression of AmCPV10-2 or AmCPV10-3 cDNA was detected. indicating that during AmCPV replication, along with functional S10 RNA, some defective variant forms of S10 RNAs are packaged in virion particles. (c) 2005 Elsevier Inc. All rights reserved.