Helitron mediated amplification of cytochrome P450 monooxygenase gene in maize

Abstract

The mass movement of gene sequences by Helitrons has significantly contributed to the lack of gene collinearity reported between different maize inbred lines. However, Helitron captured-genes reported to date represent truncated versions of their progenitor genes. In this report, we provide evidence that maize CYP72A27-Zm gene represents a cytochrome P450 monooxygenase (P450) gene recently captured by a Helitron and transposed into an Opie-2 retroposon. The four exons of the CYP72A27 gene contained within the element contain a putative open reading frame (ORF) for 428 amino acid residues. We provide evidence that Helitron captured CYP72A27-Zm is transcribed. To identify the progenitor gene and the evolutionary time of capture, we searched the plant genome database and discovered other closely related CYP72A27-Zm genes in maize and grasses. Our analysis indicates that CYP72A27-Zm represents an almost complete copy of maize CYP72A26-Zm gene captured by a Helitron about 3.1 million years ago (mya). The Helitron-captured gene then duplicated twice, approximately 1.5-1.6 mya giving rise to CYP72A36-Zm and CYP72A37-Zm. These data provide evidence that Helitrons can capture and mobilize intact genes that are transcribed and potentially encode biologically relevant proteins.