Li KL, Nakashima K, Inoue J, Satoh N.

Genes (Basel). 2020 Aug 13;11(8):937. doi:10.3390/genes11080937

Phylogenetic Analyses of Glycosyl Hydrolase Family 6 Genes in Tunicates: Possible Horizontal Transfer.

Comparison of primary sequence and of intron position suggests that GHC6-1 was transferred in a common ancestor of all living tunicates. O. dioica's GH6-1 gene lacks a conserved catalytic aspartate, and does not share introns with the other tunicate genes.

“We found that in many tunicate GH6-1 proteins, an aspartic acid can be aligned to the catalytic H. jecorina D221, except for SthGH6-1b (E197) and OdiGH6-1 (K211). However, the catalytic aspartic acid was not conserved in tunicate CesA.”

“In this study, although we found no other sites shared between genes of O. dioica and other tunicates, we found that many shared splice sites are present among GH6-containing genes from three other major clades of tunicates (Thaliacea + Phlebobranchia + Stolidobranchia). It is reasonable to assume that many shared introns were acquired after the branching of larvaceans and before the subsequent divergence of major tunicate clades.”