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Plant Physiology 138:600-610 (2005) © 2005 American Society of Plant Biologists Genome Organization of More Than 300 Defensin-Like Genes in Arabidopsis1,[w]Department of Plant Biology, University of Minnesota, St. Paul, Minnesota 55108
Defensins represent an ancient and diverse set of small, cysteine-rich, antimicrobial peptides in mammals, insects, and plants. According to published accounts, most species' genomes contain 15 to 50 defensins. Starting with a set of largely nodule-specific defensin-like sequences (DEFLs) from the model legume Medicago truncatula, we built motif models to search the near-complete Arabidopsis (Arabidopsis thaliana) genome. We identified 317 DEFLs, yet 80% were unannotated at The Arabidopsis Information Resource and had no prior evidence of expression. We demonstrate that many of these DEFL genes are clustered in the Arabidopsis genome and that individual clusters have evolved from successive rounds of gene duplication and divergent or purifying selection. Sequencing reverse transcription-PCR products from five DEFL clusters confirmed our gene predictions and verified expression. For four of the largest clusters of DEFLs, we present the first evidence of expression, most frequently in floral tissues. To determine the abundance of DEFLs in other plant families, we used our motif models to search The Institute for Genomic Research's gene indices and identified approximately 1,100 DEFLs. These expressed DEFLs were found mostly in reproductive tissues, consistent with our reverse transcription-PCR results. Sequence-based clustering of all identified DEFLs revealed separate tissue- or taxon-specific subgroups. Previously, we and others showed that more than 300 DEFL genes were expressed in M. truncatula nodules, organs not present in most plants. We have used this information to annotate the Arabidopsis genome and now provide evidence of a large DEFL superfamily present in expressed tissues of all sequenced plants.
1 This work was supported by a National Science Foundation Plant Genome Research Program award on Medicago truncatula genomics (DBI no. 0110206; Principal Investigator Douglas R. Cook) and by funds from the University of Minnesota College of Biological Sciences. 2 These authors contributed equally to the paper. [w] The online version of this article contains Web-only data. www.plantphysiol.org/cgi/doi/10.1104/pp.105.060079. * Corresponding author; e-mail kvandenb{at}cbs.umn.edu; fax 612–625–1738. Received January 25, 2005; returned for revision March 4, 2005; accepted March 9, 2005. This article has been cited by other articles:
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