Review on Mechanism of DNA Sequencing Technologies in Crop Improvement

The development of DNA sequencing strategies has been a high priority in genetics research since the discovery of the structure of DNA and the basic molecular mechanisms of heredity.However, it was not until the works by Maxam and Gilbert (1977), and Sanger (Sanger et al, 1977), that the first practical sequencing methods were developed and implemented on a large scale.The first isolation and sequencing of a plant cDNA by Bedbrook and colleagues a few years later initiated the field of Plant Molecular Genetics (Bedbrook et al, 1980).Plant biotechnology started shortly thereafter with the successful integration of recombinant DNA and sequencing techniques to generate the first transgenic plants using Agrobacterium (Fraley et al, 1983; Herrera Estrella et al, 1983).The first genetic map in plants based on restriction fragment length polymorphisms (RFLPs; Bernatzky & Tanksley, 1986) enabled the capture of genetic variation and started the era of molecular markerassisted plant breeding.Since then, sequencing methodologies have been essential tools in plant research.They have allowed the characterization and modification of genes and metabolic pathways, as well as the use of genetic variation for studies in species diversity, marker-assisted selection (MAS), germplasm characterization and seed purity.The determination of the reference genomes in Arabidopsis thaliana, rice and maize using Sanger sequencing strategies constituted major milestones that enabled the analysis of genome architecture and gene characterization in plants (The Arabidopsis Genome Initiative, 2001; International Rice Genome Project, 2005; Schnable et al, 2009).More recently, the development and increasing availability of multiple Next-Generation sequencing (NGS) technologies minimized research limitations and bottlenecks based on sequence information (Metzker, 2010; Glenn, 2011).It is difficult to overstate the influence that these massively parallel systems have had in our understanding of plant genomes and in the expansion, acceleration and diversification of breeding and biotechnology projects.At the same time, this influence tends to understate the importance that capillary Sanger sequencing still has in day-by-day research and development work.This review provides a description of major sequencing technologies that are developed through time.