Yan Jian, Aboshi Takako, Teraishi Masayoshi, Strickler Susan R, Spindel Jennifer E, Tung Chih-Wei, Takata Ryo, Matsumoto Fuka, Maesaka Yoshihiro, McCouch Susan R, Okumoto Yutaka, Mori Naoki, Jander Georg
Boyce Thompson Institute for Plant Research, Ithaca, New York 14853.
Graduate School of Agriculture, Kyoto University, Kyoto 808-8502, Japan.
Plant Cell. 2015 Apr;27(4):1265-78. doi: 10.1105/tpc.15.00058. Epub 2015 Apr 21.
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)-β-tyrosine, an isomer of the common amino acid (S)-α-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 β-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 β-tyrosine production in Nipponbare. Rice cultivars that do not produce β-tyrosine have a chromosome 12 deletion that encompasses TAM1. Although β-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 β-tyrosine concentrations. In contrast, root growth of Arabidopsis thaliana and other tested dicot plants was inhibited by concentrations as low as 1 μM. As β-tyrosine is exuded into hydroponic medium at higher concentrations, it may contribute to the allelopathic potential of rice.
非蛋白质氨基酸通常是标准的20种蛋白质氨基酸的异构体,在许多植物物种中具有与防御相关的功能。对栽培水稻(Oryza sativa)中茉莉酸诱导的代谢产物进行的靶向搜索,在日本晴品种的种子、叶片、根和根分泌物中鉴定出了(R)-β-酪氨酸,它是常见氨基酸(S)-α-酪氨酸的异构体。对119个不同品种的检测显示出明显的存在/缺失多态性,β-酪氨酸在温带粳稻品种中最为普遍。遗传图谱分析在12号染色体上鉴定出一个候选基因,通过在本氏烟草中的瞬时表达和体外酶活性测定,证实该基因编码酪氨酸氨基变位酶(TAM1)。TAM1中的一个点突变消除了日本晴中β-酪氨酸的产生。不产生β-酪氨酸的水稻品种在12号染色体上有一个包含TAM1的缺失。尽管β-酪氨酸的积累是由植物防御信号分子茉莉酸诱导的,但对半翅目和鳞翅目食草动物的生物测定表明,在生理相关的β-酪氨酸浓度下没有负面影响。相比之下,低至1μM的浓度就会抑制拟南芥和其他受试双子叶植物的根生长。由于β-酪氨酸以较高浓度分泌到水培介质中,它可能有助于水稻的化感潜力。