The assembly of Y chromosome reveals amplification of genes regulating male fertility in Bactrocera dorsalis

The oriental fruit fly Bactrocera dorsalis is an invasive pest causing considerable ecological and economic damage worldwide.The Y chromosome is an important target for the Sterile Insect Technique (SIT), but its sequence and structure has been poorly explored.We assembled the genome of B. dorsalis at the chromosome level with a total size of 590 Mb.The assembly includes a 7.96 Mb Y chromosome sequence, being the first reported Y chromosome in Tephritidae.The assembled Y chromosome is highly repetitive, and 19 genes are annotated manually.We surprisingly found that the M factor (MoY) in Tephritidae has multiple copies on the Y chromosome.Besides, we identified 17 copies of typo-gyf that were specific highly expressed in testis.RNAi targeting the typo-gyf resulted in depletion of live sperms, suggesting that the amplification of typo-gyf is essential for male fertility, which provides insight into the reproductive biology of this invasive insect.Our results will also provide target genes for CRISPR/Cas9 based SIT, leading to the development of novel control strategies against tephritid flies.