The Tyrosine Aminomutase TAM1 Is Required for β-Tyrosine Biosynthesis in Rice

Abstract

ORCID IDs: 0000-0001-8597-9841 (J.Y.); 0000-0002-0121-0048 (S.R.S.); 0000-0002-9675-934X (G.J.)Non-protein amino acids, often isomers of the standard 20 protein amino acids, have defense-related functions in many plant species. A targeted search for jasmonate-induced metabolites in cultivated rice (Oryza sativa) identified (R)-b-tyrosine, an isomer of the common amino acid (S)-a-tyrosine in the seeds, leaves, roots, and root exudates of the Nipponbare cultivar. Assays with 119 diverse cultivars showed a distinct presence/absence polymorphism, with b-tyrosine being most prevalent in temperate japonica cultivars. Genetic mapping identified a candidate gene on chromosome 12, which was confirmed to encode a tyrosine aminomutase (TAM1) by transient expression in Nicotiana benthamiana and in vitro enzyme assays. A point mutation in TAM1 eliminated b-tyrosine production in Nipponbare. Rice cultivars that do not produce b-tyrosine have a chromosome 12 deletion that encompasses TAM1. Although b-tyrosine accumulation was induced by the plant defense signaling molecule jasmonic acid, bioassays with hemipteran and lepidopteran herbivores showed no negative effects at physiologically relevant b-tyrosine concentrations. In contrast, root growth of Arabidopsis thaliana and other tested dicot plants was inhibited by concentrations as low as 1 mM. As b-tyrosine is exuded into hydroponic medium at higher concentrations, it may contribute to the allelopathic potential of rice.

Ethylene signaling regulates natural variation in the abundance of antifungal acetylated diferuloylsucroses and Fusarium graminearum resistance in maize seedling roots

“…Natural variation in metabolic traits is often caused by cis polymorphisms in metabolic enzyme‐encoding genes (Meihls et al ., ; Yan et al ., ; Handrick et al ., ). However, we found no predicted acetyltransferase gene within our QTL interval.…”

Natural variation of plant metabolism: genetic mechanisms, interpretive caveats, evolutionary and mechanistic insights.

“…These include the advent of rapid metabolomic platforms allowing the quantification of hundreds to thousands of metabolites in as many different genotypes (Fiehn, 2001;Meyer et al, 2007;Fiehn et al, 2008). In combination with the ability to sequence and measure the transcriptome of all of these same lines, there is a massive influx of studies reporting on the identification of causal genes controlling the variation in metabolites in numerous species, from crop plants like maize (Zea mays), rice (Oryza sativa), and tomato (Solanum lycopersicum) to models like Arabidopsis (Arabidopsis thaliana) and ecological models like Boechera stricta and Nicotiana attenuata (Fu and Xue, 2010;Hartings et al, 2011;Li et al, 2011Li et al, , 2015Kausch et al, 2012;Prasad et al, 2012;Matsuba et al, 2013;Chang et al, 2015;Yan et al, 2015). These studies provide new insights into the mechanistic and evolutionary structures that influence how plant metabolism functions within a broader context.…”

Get Tough, Get Toxic, or Get a Bodyguard: Identifying Candidate Traits Conferring Belowground Resistance to Herbivores in Grasses

“…M -tyrosine can reach concentrations of up to 43% of root exudate dry matter in some Festuca species, is allelopathic (Bertin et al, 2007) and can reduce cabbage looper ( Trichoplusia ni ) growth rates when expressed in Arabidopsis thaliana (Huang, 2010). Another tyrosine isomer, β-tyrosine, is inducible, and abundant in the roots and root exudates of some rice cultivars, but despite also being strongly allelopathic has no detectable effects on hemipteran or lepidopteran herbivores in bioassays (Yan et al, 2015). …”