Flower color breeding by molecular design in ornamentals

Chinese. 花色是观赏植物最重要的观赏性状之一，基因工程改良花色是一条重要的育种途径之一。观赏植物的花色素由类黄酮、类胡萝卜素及其他色素组成，且类黄酮是大多数花色形成的决定性色素群。目前，花青素苷生物合成途径已经解析，经过该途径合成的天竺葵色素苷、矢车菊色素苷和飞燕草色素苷是形成有色花的主要色素物质，其中飞燕草色素苷是重要的蓝色花色素成分。本文归纳了利用基因工程改良花色的最新进展，尤其对于蓝色香石竹以及蓝色月季的分子育种进行了介绍。此外，基于目前对花色关键结构基因功能的了解，本文分析了蓝紫色花、白色-浅粉色花、黄色花、橙红色-红色花以及彩斑的花色呈色机理，并提出了利用基因工程手段改良这些花色的分子策略，即通过导入外源基因，使其异源表达或抑制内源基因的表达来调控花色的改变。此外，本文还对基因资源的选择，转基因后外源基因与内源基因的互作关系以及转基因植株花色的稳定性进行了讨论，以期为定向改良观赏植物花色性状奠定基础。

English. Flower color is one of the most important ornamental characteristics. Modification of flower color by genetic engineering would be the important breeding approach. Basically, flower color pigments of ornamental plant are composed of flavonoid, carotenoid and other pigments, it is well known that the flavonoid would be the dominant component for determining the flower coloring. So far, the biosynthetic pathways of anthocyanin has been already clear, and the pigments of pelargonidin 3-O-glucoside, cyanidin 3-O-glucoside and delphinidin 3-O-glucoside, which synthesized in the anthocyanin biosynthetic pathway, are the major determinant factors for flower color formation, for example, delphinidin 3-O-glucoside is an important composition in blue flower. In this review, we summarized the latest advances in flower color modification by genetic engineering approaches and especially introduced the breeding of blue carnation and blue rose by molecular approaches. And also we discussed the coloration mechanism of blue-violet flowers, white-shallow pink flowers, yellow flowers, bronze-red flower and color spots based on the knowledges of key flower color structural genes＇ function, then advanced the molecular strategies for flower color modification by molecular design via genetic engineering approaches, which might be through the introduction gene to heterologous expression or inhibition of endogenous gene expression to control flower color changes. Additional, we further discussed the strategies for gene selection, integration for exogenous and endogenous gene and stabilities of transgenic flower color, which might be much more helpful for breeding program in ornamental flower color.