Transposition of a Rice Mutator-Like Element in the Yeast Saccharomyces cerevisiae

Abstract

(N.J.)Mutator-like transposable elements (MULEs) are widespread in plants and are well known for their high transposition activity as well as their ability to duplicate and amplify host gene fragments. Despite their abundance and importance, few active MULEs have been identified. In this study, we demonstrated that a rice (Oryza sativa) MULE, Os3378, is capable of excising and reinserting in yeast (Saccharomyces cerevisiae), suggesting that yeast harbors all the host factors for the transposition of MULEs. The transposition activity induced by the wild-type transposase is low but can be altered by modification of the transposase sequence, including deletion, fusion, and substitution. Particularly, fusion of a fluorescent protein to the transposase enhanced the transposition activity, representing another approach to manipulate transposases. Moreover, we identified a critical region in the transposase where the net charge of the amino acids seems to be important for activity. Finally, transposition efficiency is also influenced by the element and its flanking sequences (i.e., small elements are more competent than their large counterparts). Perfect target site duplication is favorable, but not required, for precise excision. In addition to the potential application in functional genomics, this study provides the foundation for further studies of the transposition mechanism of MULEs.

Functional characterization of the active Mutator-like transposable element, Muta1 from the mosquito Aedes aegypti

“…In prior studies members of five superfamilies (MULE, Tc1/mariner, hAT, PIF/Harbinger and piggyBac ) were shown to transpose in yeast [15, 35–38]. Our yeast assay consisted of two plasmid constructs: an expression vector containing the Muta1 transposase coding sequence downstream of the galactose inducible GAL1 promoter, and a reporter vector containing a nonautonomous element inserted in, and blocking expression of, the ADE2 gene (Additional file 4: Figure S3A).…”

“…Nonautonomous family members often contain a variety of sequences between the TIRs, including fragments from host genes; such elements are called Pack-MULEs [11]. To date, only a few active MULEs have been identified, including MuDR , Hop1 , Jittery, TED , and Os3378 [6, 12–15]. Importantly, only the rice Os3378 element has been shown to transpose in a heterologous host [15].…”

“…To date, only a few active MULEs have been identified, including MuDR , Hop1 , Jittery, TED , and Os3378 [6, 12–15]. Importantly, only the rice Os3378 element has been shown to transpose in a heterologous host [15]. …”

Rice MULEs Transpose in Yeast

“…Fusion of EYFP at the C terminus induced aggregates in cytoplasm. (Reprinted from Zhao et al [2015], Figure 6. ) www.plantcell.org/cgi/doi/10.1105/tpc.114.136143…”

“…To this end, Zhao et al (2015) used the Os3378 MULE from rice to recapitulate transposition in yeast (Saccharomyces cerevisiae). They first isolated a full-length element that encodes a functional transposase, by examining cDNAs and comparing genomic sequences and secondary structures of active MULEs from multiple species.…”