Melanization in living organisms: a perspective of species evolution

Eumelanin is a heteropolymer that is generally composed of hydroxylated indole residues and plays diverse protective functions in various species.Melanin is derived from the amino acid tyrosine and production of melanin is a highly complex oxidative process with a number of steps that can either proceed enzymatically or non-enzymatically.Although melanin plays important protective roles in many species,during melanization,particularly in steps that can proceed non-enzymatically,many toxic intermediates are produced,including semiquinones,dopaquinone,indole-quinones and moreover,the production of many reactive oxygen species.To mitigate the production of reactive species,a number of proteins that regulate the biochemical process of melanization have evolved in various living species,which is closely related to adaptation and physiological requirements.In this communication,we discuss differences between non-enzymatic and enzymatic processes of melanization and the enzymatic regulation of melanization in difference species with an emphasis on differences between mammals and insects.Comparison between melanization and insect sclerotization is also emphasized which raises some interesting questions about the current models of these pathways.

Construction of an efficient genomic editing system with CRISPR/Cas9 in the vector mosquito Aedes albopictus

Aedes (Stegomyia) albopictus, also known as the Asian tiger mosquito, is a mosquito which originated in Asia. In recent years, it has become increasingly rampant throughout the world. This mosquito can transmit several arboviruses, including dengue, Zika and chikungunya viruses, and is considered a public health threat. Despite the urgent need of genome engineering to analyze specific gene functions, progress in genetical manipulation of Ae. albopictus has been slow due to a lack of efficient methods and genetic markers. In the present study, we established targeted disruptions in two genes, kynurenine hydroxylase (kh) and dopachrome conversion enzyme (yellow), to analyze the feasibility of generating visible phenotypes with genome editing by the clustered regularly interspaced short palindromic repeats (CRISPR)/ CRISPR-associated protein 9 (Cas9) system in Ae. albopictus. Following Cas9 single guide RNA ribonucleoprotein injection into the posterior end of pre-blastoderm embryos, 30%-50% of fertile survivors produced alleles that failed to complement existing kh and yellow mutations. Complete eye and body pigmentation defects were readily observed in GI pupae and adults, indicating successful generation of highly heritable mutations. We conclude that the CRISPR/Cas9-mediated gene editing system can be used mAe. albopictus and that it can be adopted as an efficient tool for genome-scale analysis and biological study.