Genome-wide analysis identifies gain and loss/change of function within the small multigenic insecticidal Albumin 1 family of Medicago truncatula

• DOI: 10.1186/s12870-016-0745-0
• Publication Date: 2016-03-10T11:11:07Z
• Authors: L. Karaki; P. Da Silva; F. Rizk; C. Chouabe; N. Chantret; V. Eyraud; F. Gressent; C. Sivignon; I. Rahioui; D. Kahn; C. Brochier-Armanet; Y. Rahbé; C. Royer
• Keywords: Medicago truncatula

Albumin 1b peptides (A1b) are small disulfide-knotted insecticidal produced by Fabaceae (also called Leguminosae). To date, their diversity among this plant family has been essentially investigated through biochemical and PCR-based approaches. The availability of high-quality genomic resources for several fabaceae species, which the model species Medicago truncatula (Mtr), allowed a analysis protein aimed at i) deciphering evolutionary history A1b proteins links with A1b-nodulins that short non-insecticidal disulfide-bonded involved in root nodule signaling ii) exploring functional novel bioactive molecules. Investigating Mtr genome revealed remarkable expansion, mainly tandem duplications, albumin1 (A1) genes, retaining nearly all same canonical structure both gene levels. Phylogenetic ancestral molecule was most probably giving rise to, others, A1b-nodulins. Expression meta-analysis many coding genes silent wide tissue distribution A1 transcripts/peptides within organs. Evolutionary rate analyses highlighted branches sites positive selection signatures, including two shown to be critical activity. Seven were chemically synthesized folded vitro, then assayed biological Among these, AG41 (aka MtrA1013 isoform, encoded orphan TA24778 contig.), showed an unexpectedly high study highlights unique burst genus compared other taxa full-genomes available: no member Lotus, or red clover while only few present chick pea, soybean pigeon pea genomes. expansion is reminiscent situation described another disulfide-rich peptide family, “Nodule-specific Cysteine-Rich” (NCR), discovered species. oldest toxin from Sophorae, dating birth seed-defense function more than 58 million years, making plant/insect toxin/receptor (A1b/insect v-ATPase) one known.