Chromosome-level genome assembly provides insights into adaptive evolution of chromosome and important traits in the gecko Gekko japonicus

Abstract

Gekko japonicus possess excellent flexible climbing and detoxification ability under insectivorous habits, and its chromosomes and the genetic evolutionary mechanisms behind these traits are still unclarified. Here, we assembled a chromosome-level genome of G. japonicus with a total size of 2.53 Gb contained in 19 pairs of chromosomes. The evolutionary breakpoint regions (EBRs) are significantly enriched for some repetitive elements compared to the rest of genome and the genes located in the EBRs are enriched in defense response pathway. G. japonicus specific gene families, expanded gene families and positively selected genes are mainly enriched in some pathways related to the immune, sensory and nervous systems. These results from comprehensive comparative genomics and evolutionary genomics analyses indicated that bitter taste receptor type 2 (T2Rs) expanded in different lineages by tandem gene duplication. The expansion and independent duplication events of T2Rs and positively selected branches were predominantly present in insectivorous species, suggests that T2Rs are associate with clearance of bitter toxins in gekkotans. Detoxification genes in detox and biosynthetic cytochrome P450 of G. japonicas have frequent duplication and loss events, suggests that they undergo more birth and death processes compared to biosynthesis type genes. Pro, Cys, Gly and Ser are the most abundant amino acids in 66 epidermis formation corneous beta proteins (CBPs) of G. japonicas, the abundance of Gly and Cys in CBPs implying significant effects on the flexibility and setae adhesiveness of gekkotans. Some thermosensitive thermoregulatory transient receptor potential channels under relaxed purifying selection or positive selection in G. japonicus, implying that one of the important factors improve the ability to adapt to climate change.