Genomic clustering of cyanogenic glucoside biosynthetic genes aids their identification in Lotus japonicus and suggests the repeated evolution of this chemical defence pathway

Abstract

SUMMARYCyanogenic glucosides are amino acid-derived defence compounds found in a large number of vascular plants. Their hydrolysis by specific b-glucosidases following tissue damage results in the release of hydrogen cyanide. The cyanogenesis deficient1 (cyd1) mutant of Lotus japonicus carries a partial deletion of the CYP79D3 gene, which encodes a cytochrome P450 enzyme that is responsible for the first step in cyanogenic glucoside biosynthesis. The genomic region surrounding CYP79D3 contains genes encoding the CYP736A2 protein and the UDP-glycosyltransferase UGT85K3. In combination with CYP79D3, these genes encode the enzymes that constitute the entire pathway for cyanogenic glucoside biosynthesis. The biosynthetic genes for cyanogenic glucoside biosynthesis are also co-localized in cassava (Manihot esculenta) and sorghum (Sorghum bicolor), but the three gene clusters show no other similarities. Although the individual enzymes encoded by the biosynthetic genes in these three plant species are related, they are not necessarily orthologous. The independent evolution of cyanogenic glucoside biosynthesis in several higher plant lineages by the repeated recruitment of members from similar gene families, such as the CYP79s, is a likely scenario.

Comparative Analysis of Benzoxazinoid Biosynthesis in Monocots and Dicots: Independent Recruitment of Stabilization and Activation Functions

“…Co-BX8 743 6 77 8.5 6 0.2 11.4 441 6 47 9.5 6 0.2 21.5 3168 6 549 17.6 6 1. as shown recently for cyanogenic glucoside biosynthesis by Takos et al (2011). It has been suggested that repeated recruitment might represent the majority of convergent evolution events in plant secondary metabolism (Cseke et al, 1998;Pichersky and Lewinsohn, 2011;Takos et al, 2011), and the elucidation of cyanogenesis in insects revealed convergent evolution even across the plant and animal kingdoms by recruitment of members of the same gene functions .…”

“…It has been suggested that repeated recruitment might represent the majority of convergent evolution events in plant secondary metabolism (Cseke et al, 1998;Pichersky and Lewinsohn, 2011;Takos et al, 2011), and the elucidation of cyanogenesis in insects revealed convergent evolution even across the plant and animal kingdoms by recruitment of members of the same gene functions . Although the encoded enzymes, two multifunctional P450 monooxygenases, and one UGT in plant and insect use identical substrates to synthesize the same pathway intermediates, all three genes evolved independently.…”

Two Herbivore-Induced Cytochrome P450 Enzymes CYP79D6 and CYP79D7 Catalyze the Formation of Volatile Aldoximes Involved in Poplar Defense

“…However, so far, no aldoxime dehydratases are known in plants and a BLAST search revealed no homologous genes in the P. trichocarpa genome. The third and most likely mode of volatile nitrile formation in planta is the oxidation of aldoximes by P450 enzymes of the CYP71 or CYP736 family as described for the biosynthesis of cyanogenic glycosides and camalexin (Bak et al, 1998b;Nafisi et al, 2007;Takos et al, 2011). The P. trichocarpa genome contains 25 CYP71 genes and six CYP736 genes (Nelson et al, 2008), and microarray analysis revealed that several of these genes were upregulated after herbivore feeding (Ralph et al, 2006).…”

Modularity of Plant Metabolic Gene Clusters: A Trio of Linked Genes That Are Collectively Required for Acylation of Triterpenes in Oat

“…An important discovery has been that the loci for the synthesis of avenacins are clustered. Although genes encoding plant metabolic pathways are generally regarded as randomly distributed in the genome, a growing number of plant natural product biosynthetic pathways have been identified that are encoded by operon-like gene clusters in plants (Frey et al, 1997;Gierl and Frey, 2001;Qi et al, 2004;Wilderman et al, 2004;Shimura et al, 2007;Field and Osbourn, 2008;Swaminathan et al, 2009;Chu et al, 2011;Falara et al, 2011;Field et al, 2011;Takos et al, 2011;Kliebenstein and Osbourn, 2012;Winzer et al, 2012).…”