The maize genome contains a helitron insertion.
The maize mutation sh2-7527 was isolated in a conventional maize breeding program in the 1970s. Although the mutant contains foreign sequences within the gene, the mutation is not attributable to an interchromosomal exchange or to a chromosomal inversion. Hence, the mutation was caused by an insertion. Sequences at the two Sh2 borders have not been scrambled or mutated, suggesting that the insertion is not caused by a catastrophic reshuffling of the maize genome. The insertion is large, at least 12 kb, and is highly repetitive in maize. As judged by hybridization, sorghum contains only one or a few copies of the element, whereas no hybridization was seen to the Arabidopsis genome. The insertion acts from a distance to alter the splicing of the sh2 pre-mRNA. Three distinct intron-bearing maize genes were found in the insertion. Of most significance, the insertion bears striking similarity to the recently described DNA helicase-bearing transposable elements termed HELITRONS: Like Helitrons, the inserted sequence of sh2-7527 is large, lacks terminal repeats, does not duplicate host sequences, and was inserted between a host dinucleotide AT. Like Helitrons, the maize element contains 5' TC and 3' CTRR termini as well as two short palindromic sequences near the 3' terminus that potentially can form a 20-bp hairpin. Although the maize element lacks sequence information for a DNA helicase, it does contain four exons with similarity to a plant DEAD box RNA helicase. A second Helitron insertion was found in the maize genomic database. These data strongly suggest an active Helitron in the present-day maize genome.
Lal
Shailesh K
SK
Program in Plant Molecular and Cellular Biology and Horticultural Sciences, University of Florida, Gainesville, Florida 32611-0690, USA.
Giroux
Michael J
MJ
Brendel
Volker
V
Vallejos
C Eduardo
CE
Hannah
L Curtis
LC
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D001483:Base Sequence; D004251:DNA Transposable Elements / Q000235:genetics*; D018745:Genome, Plant; D051599:Glucose-1-Phosphate Adenylyltransferase; D006824:Hybridization, Genetic; D007438:Introns; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation; D009713:Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D006109:Poaceae / Q000235:genetics; D012639:Seeds / Q000235:genetics / Q000254:growth & development; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013213:Starch / Q000096:biosynthesis; D013395:Sucrose / Q000378:metabolism; D003313:Zea mays / Q000235:genetics* / Q000254:growth & development
D004251:DNA Transposable Elements; D010940:Plant Proteins; C111076:Sh2 protein, plant; D013395:Sucrose; D013213:Starch; D009713:Nucleotidyltransferases; D051599:Glucose-1-Phosphate Adenylyltransferase