期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2020
卷号：117
期号：30
页码：18091-18098
DOI：10.1073/pnas.2010234117
出版社：The National Academy of Sciences of the United States of America
摘要：The frequent mutations recovered recently from the pollen of select maize lines resulted from the meiotic mobilization of specific low-copy number long-terminal repeat (LTR) retrotransposons, which differ among lines. Mutations that arise at male meiosis produce kernels with concordant mutant phenotypes in both endosperm and embryo because the two sperms that participate in double fertilization are genetically identical. Those are in a majority. However, a small minority of kernels with a mutant endosperm carry a nonconcordant normal embryo, pointing to a postmeiotic or microgametophytic origin. In this study, we have identified the basis for those nonconcordant mutations. We find that all are produced by transposition of a defective LTR retrotransposon that we have termed dRemp (defective retroelement mobile in pollen). This element has several unique properties. Unlike the mutagenic LTR retrotransposons identified previously, dRemp is present in hundreds of copies in all sequenced lines. It seems to transpose only at the second pollen mitosis because all dRemp insertion mutants are nonconcordant yet recoverable in either the endosperm or the embryo. Although it does not move in most lines, dRemp is highly mobile in the Corn Belt inbred M14, identified earlier by breeders as being highly unstable. Lastly, it can be recovered in an array of structures, ranging from solo LTRs to tandem dRemp repeats containing several internal LTRs, suggestive of extensive recombination during retrotransposition. These results shed further light on the spontaneous mutation process and on the possible basis for inbred instability in maize.
