Wang Lei, Albert Nick W, Zhang Huaibi, Arathoon Steve, Boase Murray R, Ngo Hanh, Schwinn Kathy E, Davies Kevin M, Lewis David H
The New Zealand Institute for Plant and Food Research Limited, Private Bag 11 600, Palmerston North, 4474, New Zealand.
Planta. 2014 Nov;240(5):983-1002. doi: 10.1007/s00425-014-2152-9. Epub 2014 Sep 3.
This study confirmed pigment profiles in different colour groups, isolated key anthocyanin biosynthetic genes and established a basis to examine the regulation of colour patterning in flowers of Cymbidium orchid. Cymbidium orchid (Cymbidium hybrida) has a range of flower colours, often classified into four colour groups; pink, white, yellow and green. In this study, the biochemical and molecular basis for the different colour types was investigated, and genes involved in flavonoid/anthocyanin synthesis were identified and characterised. Pigment analysis across selected cultivars confirmed cyanidin 3-O-rutinoside and peonidin 3-O-rutinoside as the major anthocyanins detected; the flavonols quercetin and kaempferol rutinoside and robinoside were also present in petal tissue. β-carotene was the major carotenoid in the yellow cultivars, whilst pheophytins were the major chlorophyll pigments in the green cultivars. Anthocyanin pigments were important across all eight cultivars because anthocyanin accumulated in the flower labellum, even if not in the other petals/sepals. Genes encoding the flavonoid biosynthetic pathway enzymes chalcone synthase, flavonol synthase, flavonoid 3' hydroxylase (F3'H), dihydroflavonol 4-reductase (DFR) and anthocyanidin synthase (ANS) were isolated from petal tissue of a Cymbidium cultivar. Expression of these flavonoid genes was monitored across flower bud development in each cultivar, confirming that DFR and ANS were only expressed in tissues where anthocyanin accumulated. Phylogenetic analysis suggested a cytochrome P450 sequence as that of the Cymbidium F3'H, consistent with the accumulation of di-hydroxylated anthocyanins and flavonols in flower tissue. A separate polyketide synthase, identified as a bibenzyl synthase, was isolated from petal tissue but was not associated with pigment accumulation. Our analyses show the diversity in flower colour of Cymbidium orchid derives not from different individual pigments but from subtle variations in concentration and pattern of pigment accumulation.
本研究确定了不同颜色组的色素谱，分离出关键的花青素生物合成基因，并为研究大花蕙兰花色图案的调控奠定了基础。大花蕙兰（Cymbidium hybrida）有一系列花色，通常分为四个颜色组：粉色、白色、黄色和绿色。在本研究中，对不同颜色类型的生化和分子基础进行了研究，鉴定并表征了参与类黄酮/花青素合成的基因。对选定品种的色素分析证实，矢车菊素3-O-芸香糖苷和芍药素3-O-芸香糖苷是检测到的主要花青素；花瓣组织中还存在黄酮醇槲皮素、山奈酚芸香糖苷和刺槐糖苷。β-胡萝卜素是黄色品种中的主要类胡萝卜素，而脱镁叶绿素是绿色品种中的主要叶绿素色素。花青素色素在所有八个品种中都很重要，因为花青素在花的唇瓣中积累，即使在其他花瓣/萼片中不积累。从一个大花蕙兰品种的花瓣组织中分离出编码类黄酮生物合成途径酶查尔酮合酶、黄酮醇合酶、类黄酮3'羟化酶（F3'H）、二氢黄酮醇4-还原酶（DFR）和花青素合酶（ANS）的基因。在每个品种的花芽发育过程中监测这些类黄酮基因的表达，证实DFR和ANS仅在花青素积累的组织中表达。系统发育分析表明，一个细胞色素P450序列为大花蕙兰F3'H的序列，这与花组织中二羟基化花青素和黄酮醇的积累一致。从花瓣组织中分离出一种单独的聚酮合酶，鉴定为联苄合酶，但它与色素积累无关。我们的分析表明，大花蕙兰花色的多样性不是源于不同的单个色素，而是源于色素积累浓度和模式的细微变化。
