Cockroach genomes are packed with DNA transferred by their endosymbiont bacterial partners

A groundbreaking study published in PNAS reveals that horizontal gene transfer (HGT) between insects and their bacterial partners is far more extensive than previously understood. Researchers investigated the evolutionary relationship between cockroaches and their long-standing, maternally inherited bacterial endosymbiont, Blattabacterium cuenoti. By analyzing 23 cockroach and termite genomes—including eight newly sequenced using advanced long-read technology—the team uncovered pervasive endosymbiont DNA transfer events embedded within the host genomes. The study identified a staggering 40,485 Blattabacterium-derived DNA inserts across 18 cockroach genomes, ranging from 93 to 4,900 inserts per genome. Notably, Australian panesthiine and geoscapheine cockroaches consistently harbored more than 3,000 HGT inserts. This frequency is more than an order of magnitude higher than any previous maximum estimate for HGT in eukaryotes, excluding rotifers. While past HGT research focused primarily on coding sequences, this study looked at both intra- and intergenic regions. The researchers found that roughly 75% to 85% of the transferred DNA resided in noncoding, intergenic regions, explaining why previous studies targeting only gene regions overlooked this phenomenon. The average insert size was just under 200 base pairs. Interestingly, the team discovered 32 complex "chimeric" inserts, which combined up to nine distinct, short DNA segments from different locations of the Blattabacterium genome, arranged side-by-side within the host DNA. Many of these inserts have persisted in cockroach lineages for at least 28.7 million years, strongly indicating that they provide functional, evolutionary benefits rather than being junk DNA. Because Blattabacterium reside in specialized host cells and are passed down through cockroach eggs, their close proximity during embryonic development facilitated this massive genetic integration, with potentially profound implications for host adaptation and speciation. ******************************************* Email: [email protected] #nicelang​ #news #worldnews #hotnews #science