Abstract:

The unstable mutation bz-m039 arose in a maize (Zea mays) stock that originated from a plant infected with barley stripe mosaic virus. The instability of the mutation is caused by a 3.9-kb mobile element that has been named Jittery (Jit). Jit has terminal inverted repeats (TIRs) of 181 bp, causes a 9-bp direct duplication of the target site, and appears to excise autonomously. It is predicted to encode a single 709-amino acid protein, JITA, which is distantly related to the MURA transposase protein of the Mutator system but is more closely related to the MURA protein of Mutator-like elements (MULEs) from Arabidopsis thaliana and rice (Oryza sativa). Like MULEs, Jit resembles Mutator in the length of the element's TIRs, the size of the target site duplication, and in the makeup of its transposase but differs from the autonomous element Mutator-Don Robertson in that it encodes a single protein. Jit also differs from Mutator elements in the high frequency with which it excises to produce germinal revertants and in its copy number in the maize genome: Jit-like TIRs are present at low copy number in all maize lines and teosinte accessions examined, and JITA sequences occur in only a few maize inbreds. However, Jit cannot be considered a bona fide transposon in its present host line because it does not leave footprints upon excision and does not reinsert in the genome. These unusual mobile element properties are discussed in light of the structure and gene organization of Jit and related elements.

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<em>Jittery</em>, a <em>Mutator</em> Distant Relative with a Paradoxical Mobile Behavior: Excision without Reinsertion

^{Waksman Institute, Rutgers University, Piscataway, New Jersey 08855}

^{Department of Plant Biology, Rutgers University, New Brunswick, New Jersey 08901}

^{Department of Cell and Molecular Biology, University of Rhode Island, Kingston, Rhode Island 02881}

^{These authors contributed equally to this work.}

^{Current address: Celera Genomics, 45 West Gude Drive, Rockville, MD 20850.}

^{Current address: Bone Tissue Engineering Center, Carnegie Mellon University, Pittsburgh, PA 15213.}

^{To whom correspondence should be addressed. E-mail}ude.sregtur.namskaw@renood; fax 732-445-5735.

Received 2003 Dec 5; Accepted 2004 Feb 19.

Abstract

The unstable mutation bz-m039 arose in a maize (Zea mays) stock that originated from a plant infected with barley stripe mosaic virus. The instability of the mutation is caused by a 3.9-kb mobile element that has been named Jittery (Jit). Jit has terminal inverted repeats (TIRs) of 181 bp, causes a 9-bp direct duplication of the target site, and appears to excise autonomously. It is predicted to encode a single 709–amino acid protein, JITA, which is distantly related to the MURA transposase protein of the Mutator system but is more closely related to the MURA protein of Mutator-like elements (MULEs) from Arabidopsis thaliana and rice (Oryza sativa). Like MULEs, Jit resembles Mutator in the length of the element's TIRs, the size of the target site duplication, and in the makeup of its transposase but differs from the autonomous element Mutator–Don Robertson in that it encodes a single protein. Jit also differs from Mutator elements in the high frequency with which it excises to produce germinal revertants and in its copy number in the maize genome: Jit-like TIRs are present at low copy number in all maize lines and teosinte accessions examined, and JITA sequences occur in only a few maize inbreds. However, Jit cannot be considered a bona fide transposon in its present host line because it does not leave footprints upon excision and does not reinsert in the genome. These unusual mobile element properties are discussed in light of the structure and gene organization of Jit and related elements.

Abstract

Acknowledgments

We thank Gregorio Segal and Limei He for comments on the manuscript, Junjie Li for PCR reactions in the initial phase of the project, Jerry Kermicle for teosinte seeds, Damon Lisch for alerting us to the homology between the ends of Jit and rMrh, an element which is not found in the sequence databases, and two anonymous reviewers for their constructive criticism. This research was supported by Waksman and Busch predoctoral and postdoctoral fellowships, respectively, from Rutgers University to Z.X. and X.Y., National Science Foundation Grant PCM-8007867 and USDA Grant 83-CRCR-1-1330 to J.M, and National Science Foundation Grant MCB 99-04646 and Waksman Institute start-up funds to H.K.D.

Acknowledgments

Notes

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantcell.org) is: Hugo K. Dooner (ude.sregtur.namskaw@renood).

Article, publication date, and citation information can be found at www.plantcell.org/cgi/doi/10.1105/tpc.019802.

Notes

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantcell.org) is: Hugo K. Dooner (ude.sregtur.namskaw@renood).

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