Horizontal Gene Transfer Involving Chloroplasts

Abstract

Horizontal gene transfer (HGT)- is defined as the acquisition of genetic material from another organism. However, recent findings indicate a possible role of HGT in the acquisition of traits with adaptive significance, suggesting that HGT is an important driving force in the evolution of eukaryotes as well as prokaryotes. It has been noted that, in eukaryotes, HGT is more prevalent than originally thought. Mitochondria and chloroplasts lost a large number of genes after their respective endosymbiotic events occurred. Even after this major content loss, organelle genomes still continue to lose their own genes. Many of these are subsequently acquired by intracellular gene transfer from the original plastid. The aim of our review was to elucidate the role of chloroplasts in the transfer of genes. This review also explores gene transfer involving mitochondrial and nuclear genomes, though recent studies indicate that chloroplast genomes are far more active in HGT as compared to these other two DNA-containing cellular compartments.

Keywords: HGT; chloroplast genes; cpDNA; endophytes; plants.

Figure 1

Intracellular gene transfer (IGT) and horizontal gene transfer (HGT) between two plant species. Intergenomic gene transfer represent lines in the cell from the left. Solid blue, green, and red lines depict the number of reported HGT events between cell compartments. Thicker lines indicate more frequent events than thinner lines. Dashed grey lines depict putative transfers. cp: chloroplast; mt: mitochondria; nu: nucleus.

Figure 2

Examples of HGT cases described in plant and fungi endophyte relationships [43,66,67,68,69,70,71,72,73,74,75]. FHB—Fusarium head blight.