gene is essential for the larval growth and development of silkworm, .

The genetic male sterile line () of the silkworm is a recessive mutant that is naturally mutated from the wild-type strain. One of the major characteristics of the mutant is its small larvae. Through positional cloning, candidate genes for the mutant were located in a region approximately 800.5 kb long on the 24th linkage group of the silkworm. One of the genes was CCAAT/enhancer-binding protein zeta (), which is a member of the basic region-leucine zipper transcription factor family. Compared with the wild-type strain, the mutant features a 9 bp insertion in the 3'end of open reading frame sequence of gene. Moreover, the high expression level of the gene in the testis suggests that the gene is involved in the regulation of reproduction-related genes. Using the CRISPR/Cas9-mediated knockout system, we found that the knockout strains had the same phenotypes as the mutant, that is, the larvae were small. However, the larvae of knockout strains died during the development of the third instar. Therefore, the gene was identified as the major gene responsible for mutation.