Identification of two Penelope-like elements with different structures and chromosome localization in kuruma shrimp genome.

Penelope, originally found as a key element responsible for the hybrid dysgenesis in Drosophila virilis, has been widely conserved throughout eukaryotic genomes. In other organisms, they are often referred to as Penelope-like elements or PLEs. In this study, we found two types of PLEs, designated MjPLE01 and MjPLE02, from kuruma shrimp, Marsupenaeus japonicus. There was no observed nucleotide similarity between MjPLE01 and 02, and both elements differed from each other in terms of their structure; MjPLE02 has a distinctive endonuclease (EN) domain at the C-terminus while MjPLE01 do not. A phylogenetic tree that includes publicly available PLEs and TERTs showed that MjPLE01 and 02 were closely related to Coprina elements, which have been reported as an EN-deficient PLE, and to Penelope-Poseidon group, which possess an EN domain, respectively. Genomic Southern blot analysis using MjPLE01 as a probe showed several multiple bands that differ among individual shrimps. On the other hand, two major identical bands were observed when MjPLE02 was used. Colony hybridization showed co-localization of MjPLE01 and GGTTA repeats, suggesting that MjPLE01 might be prevalent in subtelomeric regions of kuruma shrimp genome. These results suggest that the kuruma shrimp genome has at least two types of PLEs with different domain compositions, phylogenetic positions, and probably chromosomeal localization. Such distinctive types of PLEs in an organism have never been described and hence could be a potential source to understand how multiple PLE types evolved.