The iron-responsive genome of the chiton *Acanthopleura granulata*

Molluscs biomineralize structures that vary in composition, form, and function, prompting questions about the genetic mechanisms responsible for their production and the evolution of these mechanisms. Chitons (Mollusca, Polyplacophora) are a promising system for studies of biomineralization because they build a range of calcified structures including shell plates and spine- or scale-like sclerites. Chitons also harden the teeth of their rasp-like radula with a coat of iron.

Here we present the genome of the West Indian fuzzy chiton Acanthopleura granulata, the first from any aculiferan mollusc. The A. granulata genome has features that may be specialized for iron biomineralization, including a high proportion of genes regulated directly by iron and two isoforms of ferritin, one iron-regulated and the other constitutively translated.

The A. granulata genome also contains homologs of many biomineralization genes identified previously in conchiferan molluscs, suggesting the ancestral mollusc had a diverse genetic toolkit for biomineralization.