SummaryThis paper is an update of our earlier review (Jones et al., 1997, Markers and mapping: we are all geneticists now. New Phytologist 137: 165-177), which dealt with the genetics of mapping, in terms of recombination as the basis of the procedure, and covered some of the first generation of markers, including restriction fragment length polymorphisms (RFLPs), random amplified polymorphic DNA (RAPDs), simple sequence repeats (SSRs) and quantitative trait loci (QTLs). In the intervening decade there have been numerous developments in marker science with many new systems becoming available, which are herein described: cleavage amplification polymorphism (CAP), sequence-specific amplification polymorphism (S-SAP), inter-simple sequence repeat (ISSR), sequence tagged site (STS), sequence characterized amplification region (SCAR), selective amplification of microsatellite polymorphic loci (SAMPL), single nucleotide polymorphism (SNP), expressed sequence tag (EST), sequence-related amplified polymorphism (SRAP), target region amplification polymorphism (TRAP), microarrays, diversity arrays technology (DArT), single-strand conformation polymorphism (SSCP), denaturing gradient gel electrophoresis (DGGE), temperature gradient gel electrophoresis (TGGE) and methylation-sensitive PCR. In addition there has been an explosion of knowledge and databases in the area of genomics and bioinformatics. The number of flowering plant ESTs is c. 19 million and counting, with all the opportunity that this provides for gene-hunting, while the survey of bioinformatics and computer resources points to a rapid growth point for future activities in unravelling and applying the burst of new information on plant genomes. A case study is presented on tracking down a specific gene (stay-green (SGR), a post-transcriptional senescence regulator) using the full suite of mapping tools and comparative mapping resources. We end with a brief speculation on how genome analysis may progress into the future of this highly dynamic arena of plant science.
I. Introduction
BackgroundThis paper discusses advances that have been made in the field of practical gene mapping in plants since the present authors published their guide for nonspecialists, 'Markers and mapping: we are all geneticists now' (referred to here as MM1), in connection with the 2nd New Phytologist Symposium over a decade ago ( Jones et al., 1997). During this period there has been nothing short of a revolution in understanding, in technologies and in the scale of application of molecular genetics approaches to physiological and ecological problems in the plant sciences. Substantially complete and annotated sequences of the nuclear genomes of five green plant species (Arabidopsis thaliana, Oryza sativa, Populus trichocarpa, Vitis vinifera and Physcomitrella patens) are publicly available and at least as many more are well on the way to completion, including those of representative legumes (Medicago truncatula and Glycine max), major crop species (Zea mays, Solanum lycopersicum, Sorghum ...