PNAS：新品玫瑰香比茶花
研究人员近日称，茶玫瑰的独特香味来自于一个变异基因，即花中的一个基因被复制后在一个单一位点发生了变异。相关论文发表在美国《国家科学院院刊》上。过去，玫瑰园艺师将耐寒的欧洲品种同中国的月季杂交，培育出了茶玫瑰，后者更为其提供了芬芳的来源。茶玫瑰香味的主要组成部分是二甲氧基甲苯，由两个相似的酶（OOMTs）作用于化学物质地衣酚后生成。
Gabriel Scalliet领导的研究小组之前曾经发现，一些欧洲玫瑰的基因内含有与中国月季相似的酶，但是只有中国月季才能制造出这些酶。这一研究小组近日表示，区分这些酶的变异基因正是使其发生作用的关键。通过基因调控技术，研究人员回复了这两种酶的突变，结果发现酶的功能也随之发生了改变。接着，他们在5种中国月季和13种欧洲玫瑰品种中寻找相似的基因。每个玫瑰品种都拥有至少一个类OOMT基因，但是只有中国月季同时拥有两种OOMT酶。对玫瑰进化史的重建表明，第二种OOMT酶最近才出现，并且只出现于中国月季中。研究人员称它的出现来自于对第一种酶的复制。（来源：Eurekalert！中文版）
生物谷推荐原始出处：
（PNAS），10.1073/pnas.0711551105，Gabriel Scalliet, Philippe Hugueney
Scent evolution in Chinese roses
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Laboratoire Reproduction et Développement des Plantes, Institut Fédératif de Recherche 128, Unité Mixte de Recherche 5667, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Lyon 1, Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, 69364 Lyon Cedex 07, France; Laboratoire d'Ecologie des Hydrosystèmes Fluviaux, Unité Mixte de Recherche 5023, Centre National de la Recherche Scientifique, Université Lyon 1, 43 Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex, France; ¶Laboratoire de Cristallographie et RMN Biologique, Unité Mixte de Recherche 8015, Centre National de la Recherche Scientifique-Faculté de Pharmacie, 4 Avenue de l'Observatoire, case 48, 75270 Paris Cedex 06, France; and ||Laboratoire de Biotechnologies Végétales Appliquées aux Plantes Aromatiques et Médicinales, EA3061, Université Jean Monnet, 23 Rue du Dr. Michelon, 42023 Saint-Etienne Cedex 2, France
Edited by Eran Pichersky, University of Michigan, Ann Arbor, MI, and accepted by the Editorial Board March 2, 2008 (received for review December 7, 2007)
Abstract
The phenolic methyl ether 3,5-dimethoxytoluene (DMT) is a major scent compound of many modern rose varieties, and its fragrance participates in the characteristic "tea scent" that gave their name to Tea and Hybrid Tea roses. Among wild roses, phenolic methyl ether (PME) biosynthesis is restricted to Chinese rose species, but the progenitors of modern roses included both European and Chinese species (e.g., Rosa chinensis cv Old Blush), so this trait was transmitted to their hybrid progeny. The last steps of the biosynthetic pathways leading to DMT involve two methylation reactions catalyzed by the highly similar orcinol O-methyltransferases (OOMT) 1 and 2. OOMT1 and OOMT2 enzymes exhibit different substrate specificities that are consistent with their operating sequentially in DMT biosynthesis. Here, we show that these different substrate specificities are mostly due to a single amino acid polymorphism in the phenolic substrate binding site of OOMTs. An analysis of the OOMT gene family in 18 species representing the diversity of the genus Rosa indicated that only Chinese roses possess both the OOMT2 and the OOMT1 genes. In addition, we provide evidence that the Chinese-rose-specific OOMT1 genes most probably evolved from an OOMT2-like gene that has homologues in the genomes of all extant roses. We propose that the emergence of the OOMT1 gene may have been a critical step in the evolution of scent production in Chinese roses.
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