T-DNA insertional mutagenesis

AZPIROZ, R., FELDMANN, K.A., T-DNA insertion mutagenesis in Arabidopsis Going back and forth, 1997, Trends Genet., 13 152-156. 

Walbot, V., 1992, Strategies for mutagenesis and gene cloning using transposon tagging and T-DNA insertional mutagenesis, Annu. Rev. Plant Physiol. Plant Mol. Biol. 43 49-82. 

Radhamony RN, Prasad AM, Srinivasan R (2005) T-DNA insertional mutagenesis in Arabidopsis a tool for functional genomics. Electron J Biotechnol 8(1). http //www.ejbio-technology.info/content/vol8 /issuel/fuU/4/... 

Fig. 2. Three different construct-types are used for T-DNA- or transposon-mediated insertional mutagenesis in plants. A. The knock-out construct. B. The promoter-trap construct. C. The activator construct. The solid triangles indicate either the T-DNA border repeats or the sequence repeats at the ends of a transposable element.

Mechanistically, the simplest type of mutagenesis occurs when the enzyme DNA polymerase is copying one strand of DNA into its complementary strand and places the incorrect nucleotide into the newly synthesized strand of DNA. Although it is thermodynamically favored that the correct base will be inserted, there is a lesser but real probability that the incorrect base will be inserted during DNA replication. An example would be placement of the wrong base, adenine (A), opposite the DNA base cytosine (C), instead of inserting the correct base guanine (G) opposite the base C. This results in what is described as a G/C to A/T transition mutation, and it is called a spontaneous mutation. 

Pol V is involved in other mutagenesis pathways for example, it inserts dATP opposite +BP in the G — T mutational pathway ([79], discussed below). In fact, the preferential mutagenic insertion of dATP opposite a variety of DNA lesions in E. coli has been called the A-rule ([60, 80] and references therein) and it seems likely that this is attributable to Pol V s tendency to insert dATP [37]. Based on lesion-bypass specificity, E. coli Pol V appears to be the functional ortholog of human Pol q [37], which is almost certainly responsible for correct bypass of UV lesions in human cells and minimizes UV light mutagenesis that leads to skin cancer [81-86]. 

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