Hijacking of N-fixing legume albumin-1 genes enables the cyclization and stabilization of defense peptides

Article: Journal article

Reference: Gilding, E.K., Jackson, M.A., Nguyen, L.T.T. et al. Hijacking of N-fixing legume albumin-1 genes enables the cyclization and stabilization of defense peptides. Nat Commun 15, 6565 (2024). https://doi.org/10.1038/s41467-024-50742-x

Abstract

The legume albumin-1 gene family, arising after nodulation, encodes linear a- and b-chain peptides for nutrient storage and defense. Intriguingly, in one prominent legume, Clitoria ternatea, the b-chains are replaced by domains producing ultra-stable cyclic peptides called cyclotides. The mechanism of this gene hijacking is until now unknown. Cyclotides require recruitment of ligase-type asparaginyl endopeptidases (AEPs) for maturation (cyclization), necessitating co-evolution of two gene families. Here we compare a chromosome-level C. ternatea genome with grain legumes to reveal an 8 to 40-fold expansion of the albumin-1 gene family, enabling the additional loci to undergo diversification. Iterative rounds of albumin-1 duplication and diversification create four albumin-1 enriched genomic islands encoding cyclotides, where they are physically grouped by similar pI and net charge values. We identify an ancestral hydrolytic AEP that exhibits neofunctionalization and multiple duplication events to yield two ligase-type AEPs. We propose cyclotides arise by convergence in C. ternatea where their presence enhances defense from biotic attack, thus increasing fitness compared to lineages with linear b-chains and ultimately driving the replacement of b-chains with cyclotides.

The genome sequence of the critically endangered Kroombit tinkerfrog

Type: Journal Article

Reference: Farquharson, K., McLennan, E., Belov, K., & Hogg, C. (2023). The genome sequence of the critically endangered Kroombit tinkerfrog (Taudactylus pleione). F1000Research, 12(845). https://doi.org/10.12688/f1000research.138571.1

Abstract

The Kroombit tinkerfrog (Taudactylus pleione) is a stream-dwelling amphibian of the Myobatrachidae family. It is listed as Critically Endangered and is at high risk of extinction due to chytridiomycosis. Here, we provide the first genome assembly of the evolutionarily distinct Taudactylus genus. We sequenced PacBio HiFi reads to assemble a high-quality long-read genome and identified the mitochondrial genome. We also generated a global transcriptome from a tadpole to improve gene annotation. The genome was 5.52 Gb in length and consisted of 4,196 contigs with a contig N50 of 8.853 Mb and an L50 of 153. This study provides the first genomic resources for the Kroombit tinkerfrog to assist in future phylogenetic, environmental DNA, conservation breeding, and disease susceptibility studies.