Sequencing the maize genome: Rationale, current status and future prospects

Maize is one of the important food crops and possesses one of the well-studied and most tractable genetic systems. Even though rice has been regarded as a model reference plant for genomic studies, the enormous amount of local rearrangements have distorted the local microcolinearity in maize that make rice a too distant model for map-based cloning in maize. The maize genome-sequencing project was launched on 20 September 2002 by National Science Foundation. Various sequencing techniques like methyl filtration and high CoT analysis have been standardized, both of which are based on differential methylation of gene-rich and gene-poor regions. The sequencing studies have reported that maize genome contains about 42,000-59,000 genes with average gene size of 3000-3200 bp and gene density of I per 40 to 1 per 53 bp. The information generated will help in gene identification, expression and regulation across grass genomes and also unravel the evolution of complex genomes.