Excision and reinsertion of Ac macrotransposons in maize

• Published in: Genetics (Austin) 2022-07, Vol.221 (4)
• Main Authors: Wang, Dafang, Yu, Chuanhe, Zhang, Jianbo, Peterson, Thomas
• Format: Article
• Language: English
• Subjects: Base Sequence; Corn; Deoxyribonucleic acid; DNA; DNA Transposable Elements - genetics; Evolution; Genes, Plant; Genetics; Genome, Plant; Genomes; Insertion; Investigation; Reproduction (copying); Segments; Synteny; Transposition; Zea mays - genetics
• ISSN: 1943-2631; 0016-6731; 1943-2631
• DOI: 10.1093/genetics/iyac067

Abstract Eukaryotic Macrotransposons (MTns) can be formed by 2 nearby elements flanking a segment of host DNA. The maize Ac transposon can form Ac::MTns, but little is known about Ac::MTn transposition activities. Here, we studied 3 Ac::MTns at the maize p1 locus, each of which is composed of a segment of maize p1 genomic DNA (up to 15 kb) bounded by a fractured Ac element (fAc, 2039 bp), and a full-length Ac element in direct orientation. The resulting Ac::MTns are of 16, 16.5, and 22 kb total length. From these 3 Ac::MTns, we identified 10 independent cases of macrotransposition, and observed similar features of transposition between Ac::MTn and standard Ac/Ds, including characteristic excision footprints and insertion target site duplications. Nine out of the 10 Ac::MTn reinsertion targets were genetically linked to the donor sites, another similarity with Ac/Ds standard transposition. We also identified a MTn-like structure in the maize B73 reference genome and 5 NAM founder lines. The MTn in diverse lines is flanked by target site duplications, confirming the historic occurrence of MTn transposition during genome evolution. Our results show that Ac::MTns are capable of mobilizing segments of DNA long enough to include a typical full-length plant gene and in theory could erode gene colinearity in syntenic regions during plant genome evolution. Wang et al. explore 10 independent Ac::MTn transposition events, observing similar patterns of transposition activity as compared to standard Ac transposition. They identify a case of a likely MTn in the endogenous maize B73 genome and in 5 NAM founder lines, suggesting a historic occurrence of MTn transposition. They show MTn is capable of mobilizing segments of DNA long enough to include a typical full-length plant gene and could theoretically erode gene co-linearity in syntenic regions during plant genome evolution.