Through recent government- and industry-sponsored efforts, several forward and reverse genetic screening programs have emerged over the past few years to aid in the genetic dissection of gene function in maize. Despite a US maize crop valued at $18.4 billion last year (http://www.ncga.com/03world/main/US_crop_value_2000.html) and rich genetic history, maize has taken a back seat to Arabidopsis thaliana as the model genetic system for plants over the past decade. With a fully sequenced genome, short generation time and small size, studies of Arabidopsis have provided plant scientists with a molecular framework for hormonal, developmental and environmental signaling pathways in plants. As investigations into Arabidopsis continue, our capacity to engineer biochemical pathways and alter plant physiological responses will become increasingly sophisticated. Nevertheless, approximately 130 million years have passed since monocot and higher eudicot lineages diverged. Thus, our ability to engineer agronomically important monocot grasses such as maize, rice and wheat will become increasingly limited by our lack of understanding of the physiological and morphological differences that have evolved in the monocots and higher eudicots. The sophisticated transposon collections now being generated for maize are but one of several recent projects (http://www.nsf.gov/bio/pubs/awards/genome01.htm) to provide grass researchers with essential tools for genome analysis. Because grain crops are such a closely related group, it is hoped that many of the findings made in one grass will be directly applicable to understanding the biology of another. The goal of this review is to highlight the recent developments in maize transposon-based gene characterization programs and provide a critical examination of the advantages and disadvantages each system offers.
