Meeting Abstract
The wide diversity of structures produced through biomineralization by molluscs has long been of interest to materials science. Despite technological advances, materials produced by molluscs at ambient temperature and pressure are often superior to manufactured materials in their combinations of desirable features (e.g. strength and flexibility). Chitons (Mollusca; Polyplacophora) are a promising system in which to study biomineralization because they produce a wide range of calcified structures including shell plates and sclerites. They also coat the teeth of their tongue-like radula with a range of iron oxides including magnetite. Comparative genomics permits comparisons of genetic toolkits across molluscs. Here we present the first genome of a chiton, the first from any aculiferan mollusc. We employed a hybrid assembly strategy combining Illumina and Oxford Nanopore followed by optical mapping. We produced a 605.9 Mbp assembly in 87 scaffolds with an N50 of 23.9 Mbp and a BUSCO score of 96.2%. We identified many genes hypothesized to be part of the biomineralization toolkit of conchiferan molluscs. To better understand how chitons produce iron structures, we analyzed known iron-associated proteins and located chiton-specific iron-binding regulatory sites in the untranslated regions of certain genes. We will combine further screening for iron-regulatory domains with sequencing of transcriptomes to determine gene expression patterns underlying the biomineralization of iron oxides such as magnetite. By comparing the genetic toolkits of conchiferans and aculiferans, we will be able to reconstruct the ancestral suite of biomineralization genes in molluscs. Further, by sequencing the first genome of a chiton, we are now better-positioned to study both the evolution and mechanisms of the natural production of iron structures in chitons.
