The finished sequences of the flowering plants Arabidopsis, rice, poplar, and grape; the moss Physcomitrella, and the algae Chlamydomonas have begun to allow us to understand how plant genomes share common ground with the genomes of other organisms and how they differ. In this special section, along with an online collection (www.sciencemag.org/plantgenomes), we see how current knowledge of plant genomes lends insights to investigations from biochemistry to ecosystems. Taking a comparative view of plant genomes, DellaPenna and Last (p. 479) consider how metabolic pathways are encoded in the genomes and are derived from a complex evolutionary history. Leitch and Leitch (p. 481) discuss why polyploidy is so common in plants and its evolutionary and ecological consequences. Gaut and Ross-Ibarra (p. 484) examine the evolutionary constraints on a plant's genome, with a particular focus on how genomes enlarge or shrink without changing their number of chromosomes. Tang et al. (p. 486) look at the consequences of these changes over time and how to uncover genomic changes through the examination of synteny and collinearity. Zhang (p. 489) examines the genomic landscape of epigenetics in plants. In an ecological context, Whitham et al. (p. 492) explore how the genome of a single keystone species affects interactions across communities and ecosystems. Benfey and Mitchell-Olds (p. 495) examine gene regulation from a systems network perspective and consider how natural variation and environmental inputs affect the phenotype of an individual.

ONLINE EXTRA: Explore an interactive presentation accompanying this special section on plant genomes, featuring video interviews, an interactive map, additional text and images, and an animation.

Plant genomics also brings the promise of improving crops through transgenic manipulations. But genetically modified (GM) plants have teetered between success and failure, with ethical and regulatory challenges, as well as public concerns. On p. 466 and in the online collection, Youngsteadt lays out the stats on the world's GM harvests. While GM corn and soybeans have proliferated, golden rice, engineered to combat malnutrition, has languished, Enserink reports (p. 468). As Stokstad points out (p. 472), GM papaya still struggles for worldwide acceptance, even after 10 years on the market.

Two teams have deciphered the grape's genetic code, but whether GM wine will be accepted is a lingering question, says Travis (p. 475). Kintisch explores how plant genomics can advance biofuel agriculture (p. 478). Finally, Kaiser describes how some researchers bent on using GM plants to make human proteins and other pharmaceutical products are moving indoors to allay safety concerns (p. 473). In addition to these overviews, see the associated Editorial by Fedoroff and the Science Careers article by Williams, as well as reports by Field and Osbourn (p. 543), Baerenfaller et al. (www.sciencemag.org/cgi/content/full/1157956/DC1), and Dinneny et al . Given what has been learned so far from a variety of plant genomes, we eagerly look ahead to a growing field.