Zer Hagit, Mizrahi Hila, Malchenko Nikol, Avin-Wittenberg Tamar, Klipcan Liron, Ostersetzer-Biran Oren
Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel.
Institute of Plant Sciences, the Gilat Research Center, Agricultural Research Organization (ARO), Negev, Israel.
Front Plant Sci. 2020 Mar 6;11:140. doi: 10.3389/fpls.2020.00140. eCollection 2020.
Plants produce a myriad of specialized (secondary) metabolites that are highly diverse chemically, and exhibit distinct biological functions. Here, we focus on -tyrosine (-tyrosine), a non-proteinogenic byproduct that is often formed by a direct oxidation of phenylalanine (Phe). Some plant species (e.g., and ) produce and accumulate high levels of -tyrosine in their root-tips enzymatic pathways. Upon its release to soil, the Phe-analog, -tyrosine, affects early post-germination development (i.e., altered root development, cotyledon or leaf chlorosis, and retarded growth) of nearby plant life. However, the molecular basis of -tyrosine-mediated (phyto)toxicity remains, to date, insufficiently understood and are still awaiting their functional characterization. It is anticipated that upon its uptake, -tyrosine impairs key metabolic processes, or affects essential cellular activities in the plant. Here, we provide evidences that the phytotoxic effects of -tyrosine involve two distinct molecular pathways. These include reduced steady state levels of several amino acids, and in particularly altered biosynthesis of the phenylalanine (Phe), an essential α-amino acid, which is also required for the folding and activities of proteins. In addition, proteomic studies indicate that -tyrosine is misincorporated in place of Phe, mainly into the plant organellar proteomes. These data are supported by analyses of mutants, which are affected in Phe-metabolism, as well as of mutants, which lack FtsH2, a major component of the chloroplast FtsH proteolytic machinery, which show higher sensitivity to -tyrosine. Plants treated with -tyrosine show organellar biogenesis defects, reduced respiration and photosynthetic activities and growth and developmental defect phenotypes.
植物产生大量化学性质高度多样且具有独特生物学功能的特殊（次生）代谢产物。在此，我们聚焦于对香豆酰酪氨酸（对香豆酰酪氨酸），一种非蛋白质ogenic副产物，它通常由苯丙氨酸（Phe）直接氧化形成。一些植物物种（例如，[此处原文缺失具体物种名称]和[此处原文缺失具体物种名称]）在其根尖的酶促途径中产生并积累高水平的对香豆酰酪氨酸。一旦释放到土壤中，苯丙氨酸类似物对香豆酰酪氨酸会影响附近植物生命的萌发后早期发育（即改变根系发育、子叶或叶片黄化以及生长迟缓）。然而，迄今为止，对香豆酰酪氨酸介导的（植物）毒性的分子基础仍未得到充分理解，仍有待进行功能表征。据推测，对香豆酰酪氨酸被植物吸收后会损害关键代谢过程，或影响植物细胞的基本活动。在此，我们提供证据表明对香豆酰酪氨酸的植物毒性作用涉及两条不同的分子途径。这些途径包括几种氨基酸的稳态水平降低，尤其是必需α-氨基酸苯丙氨酸（Phe）的生物合成改变，蛋白质的折叠和活性也需要苯丙氨酸。此外，蛋白质组学研究表明对香豆酰酪氨酸错误地取代苯丙氨酸掺入，主要掺入植物细胞器蛋白质组中。这些数据得到了苯丙氨酸代谢受影响的突变体以及缺乏叶绿体FtsH蛋白水解机制主要成分FtsH2的突变体分析的支持，这些突变体对香豆酰酪氨酸表现出更高的敏感性。用对香豆酰酪氨酸处理的植物表现出细胞器生物发生缺陷、呼吸和光合活性降低以及生长和发育缺陷表型。
