近日，国际著名杂志Journal of Experimental Botany在线刊登了中科院武汉植物园研究人员的最新研究成果“Introduction of apple ANR genes into tobacco inhibits expression of both CHI and DFR genes in flowers, leading to loss of anthocyanin”，文章中，研究者揭示了他们在苹果花青素形成机理研究中取得的新进展。
苹果是我国栽培面积最大、产量最多的水果，也是世界上种植面积最大的栽培果树之一。红苹果具有外观鲜艳和营养丰富的双重特点，一直以来深受人们的喜爱。红苹果呈现出的红色是花青素（anthocyanin）的大量累积形成的，同时还富含许多对人体健康有益的原花青素（Proanthocyanidin；PA）。然而，红苹果花青素的合成途径始终是现代研究的焦点，而对原花青素合成途径的研究甚少。
中科院武汉植物园果树分子育种课题组与美国伊利诺伊大学开展合作研究，通过苹果花青素还原酶（ANR）的转基因试验，发现ANR对植物花青苷、黄酮醇等类黄酮物质的合成具有调控作用。
原花青素是水果中一种重要功能性成分，由花青素还原酶（ANR）催化合成。该研究利用苹果BAC文库克隆了花青素还原酶基因（ANR）家族的两个成员，分别定位于第5、10号染色体，发现ANR基因在烟草中过量表达不仅能够抑制查尔酮异构酶基因（CHI）和二氢黄酮醇4-还原酶基因（DFR）表达，而且也影响黄酮醇合成酶基因（FLS）和无色花色素还原酶基因（LAR）的表达，最终表现为阻止花青苷的积累、改变花器官的着色方式。
研究同时还发现，苹果MdANR基因在果实发育后期的非红皮品种果皮中的表达水平高于红皮品种，揭示了ANR基因与花青苷代谢途径中的CHI、DFR等其他结构基因存在协同作用，共同调控植物花青苷、黄酮醇等类黄酮物质的合成。（生物谷Bioon.com）
doi:10.1093/jxb/err415
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Introduction of apple ANR genes into tobacco inhibits expression of both CHI and DFR genes in flowers, leading to loss of anthocyanin
Yuepeng Han1,*,†, Sornkanok Vimolmangkang2,†, Ruth Elena Soria-Guerra2,‡ and Schuyler S. Korban2,*
Three genes encoding anthocyanidin reductase (ANR) in apple (Malus×domestica Borkh.), designated MdANR1, MdANR2a, and MdANR2b, have been cloned and characterized. MdANR1 shows 91% identity in coding DNA sequences with MdANR2a and MdANR2b, while MdANR2a and MdANR2b are allelic and share 99% nucleotide sequence identity in the coding region. MdANR1 and MdANR2 genes are located on linkage groups 10 and 5, respectively. Expression levels of both MdANR1 and MdANR2 genes are generally higher in yellow-skinned cv. Golden Delicious than in red-skinned cv. Red Delicious. Transcript accumulation of MdANR1 and MdANR2 genes in fruits gradually decreased throughout fruit development. Ectopic expression of apple MdANR genes in tobacco positively and negatively regulates the biosynthesis of proanthocyanidins (PAs) and anthocyanin, respectively, resulting in white, pale pink-coloured, and white/red variegated flowers. The accumulation of anthocyanin is significantly reduced in all tobacco transgenic flowers, while catechin and epicatechin contents in transgenic flowers are significantly higher than those in flowers of wild-type plants. The inhibition of anthocyanin synthesis in tobacco transgenic flowers overexpressing MdANR genes is probably attributed to down-regulation of CHALCONE ISOMERASE (CHI) and DIHYDROFLAVONOL-4-REDUCTASE (DFR) genes involved in the anthocyanin pathway. Interestingly, several transgenic lines show no detectable transcripts of the gene encoding leucoanthocyanidin reductase (LAR) in flowers, but accumulate higher levels of catechin in flowers of transgenic plants than those of wild-type plants. This finding suggests that the ANR gene may be capable of generating catechin via an alternative route, although this mechanism is yet to be further elucidated.
