This study investigates the embryonic expression pattern of a single Euperipatoides kanangrensis (Onychophora) Toll gene. Onychophoran Toll gene expression

Recent research has shown that Toll genes, and in particular a newly defined class of Toll genes, the so-called Long Toll Genes (Loto genes), are crucial factors in embryogenesis. In arthropods, they are involved in axis formation via a process called convergent extension (CE). A hallmark of Loto genes is their relatively (compared to other Toll genes) high number of Leucine Rich Repeat elements (LRRs) and the fact that they are expressed in transverse “segmental” stripes in patterns reminiscent of classical segmentation genes such as the pair rule genes. Onychophorans represent a close outgroup to arthropods, but their embryonic development is crucially different from that of the latter. Also, it is unclear if convergent extension contributes to onychophoran germ band formation, and if so, if Loto genes are involved in governing this process. This study identifies a single Toll gene from a sequenced embryonic transcriptome that shows sequence and expression pattern characteristics of Loto genes. However, its expression pattern also comprises some general differences to arthropod Loto genes that are involved in CE.