The abnormal development of urate granules in silkworm larvae leads to translucent mutants with a distinct transparent phenotype. Studies on such mutants are expected to enhance current understanding of uric acid metabolism. The hoarfrost translucent (oh) mutant exhibits a mottled, translucent larval integument due to the presence of smaller and irregularly shaped urate granules compared to wild-type individuals. Uric acid content in the silkworm larval integuments is significantly lower in the oh mutant. Using positional cloning, we successfully narrowed a ~ 180 kb region linked to the oh locus and identified the candidate gene, Bmpallidin, encoding the biosynthesis of lysosome-related organelles complex 1 subunit 6. Three alternative splicing isoforms were identified
Only isoform II was predicted to translate normally and was drastically reduced at both mRNA and protein levels in the oh mutant. Conversely, the non-functional isoform III showed slightly increased expression in the mutant. An 860 bp genomic sequence in the wild type was replaced by a 30 bp sequence in the mutant. Knockdown of Bmpallidin induced a translucent phenotype in first-instar larvae. These findings conclude that Bmpallidin is responsible for the oh mutant phenotype and plays a crucial role in urate granules formation in silkworms.