# Plasmodium LCCL domain-containing modular proteins have their origins in the ancestral alveolate

## TL;DR

This study shows that Plasmodium proteins crucial for malaria transmission originated in a common ancestor of a broader group of organisms called alveolates.

## Contribution

The study reveals that LCCL lectin domain adhesive-like proteins predate the Apicomplexa and Alveolata lineages.

## Key findings

- LAP orthologues are conserved in all apicomplexans with lineage-specific gene loss and duplication.
- LAPs are found in chromerids and predatory colponemids but absent in other alveolate lineages.
- The LCCL domain-containing proteins originated in the ancestral alveolate.

## Abstract

Plasmodium species encode a unique set of six modular proteins named LCCL lectin domain adhesive-like proteins (LAPs) that operate as a complex and that are essential for malaria parasite transmission from mosquito to vertebrate. LAPs possess complex architectures obtained through unique assemblies of conserved domains associated with lipid, protein and carbohydrate interactions, including the name-defining LCCL domain. Here, we assessed the prevalence of Plasmodium LAP orthologues across eukaryotic life. Our findings show orthologous conservation in all apicomplexans, with lineage-specific repertoires acquired through differential lap gene loss and duplication. Besides Apicomplexa, LAPs are found in their closest relatives: the photosynthetic chromerids, which encode the broadest repertoire including a novel membrane-bound LCCL protein. LAPs are notably absent from other alveolate lineages (dinoflagellates, perkinsids and ciliates), but are encoded by predatory colponemids, a sister group to the alveolates. These results reveal that the LAPs are much older than previously thought and pre-date not only the Apicomplexa but the Alveolata altogether.