The sequenced genome and the leaf transcriptome of a near relative of Abrus pulchellus and Abrus precatorius was analyzed to characterize the genetic basis of toxin gene expression. From the high-quality genome assembly, a total of 26 potential coding regions were identified that contain genes with abrin-like, pulchellin-like, and agglutinin-like homology, with full-length transcripts detected in leaf tissue for 9 of the 26 coding regions. All of the toxin-like genes were identified within only five isolated regions of the genome, with each region containing 1 to 16 gene variants within each genomic region (<1 Mbp). The Abrus precatorius cultivar sequenced here contains genes which encode for proteins that are homologous to certain abrin and prepropulchellin genes previously identified, and we observed substantial diversity of genes and predicted gene products in Abrus precatorius and previously characterized toxins. This suggests diverse toxin repertoires within Abrus, potentially the results of rapid toxin evolution.
Keywords: Abrus precatorius; Iso-Seq; abrin; full genome sequencing; genome assembly; isoform; pulchellin; toxin evolution.