Genome Characteristics and ODVs Proteome of a Second Distinct Alphabaculovirus from Spodoptera litura

Background: Spodoptera litura is a harmful pest that feeds on over 80 species of plants, which can be infected and killed by Spodoptera litura nucleopolyhedrovirus (SpltNPV). SpltNPV-C3 is a clone from type C SpltNPV, observed and collected in Japan. Compared with type A or type B SpltNPV, SpltNPV-C3 can cause rapid mortality of S. litura larvae. Methods: In this research, occlusion bodies (OBs) and occlusion-derived viruses (ODVs) of SpltNPV-C3 were purified, and OBs were observed under a scanning electron microscope (SEM). ODVs were observed under a transmission electron microscope (TEM). Results: Both of OBs and ODVs show typical nucleopolyhedrovirus (NPV) morphological characteristics.The genome of SpltNPV-C3 was sequenced and analyzed, and the total length was 148,634 bp (GenBank accession:780426 which was submitted as SpltNPV-Ⅱ) with a G+C content of 45%. A total of 149 ORFs were determined to encode ORFs. Based on the core genes of baculovirus, a phylogenetic tree of 90 baculoviruses was constructed. LC‒MS/MS was used to analyze the proteins of SpltNPV-C3; 34 proteins were found in the purified ODVs, 15 of which were core proteins. The complexes of Per os infectivity factors 1, 2, 3 and 4 (PIF-1, 2, 3 and 4) were predicted with the help of the AlphaFold multimer and predicted conserved sequences in PIF-3. SpltNPV-C3 is a valuable species because of its virulence, and this research will be beneficial for pest control by analyzing the genome and proteins of SpltNPV-C3.