近日，國際著名雜志Journal of Experimental Botany在線刊登了中科院武漢植物園研究人員的最新研究成果“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,，研究者揭示了他們在蘋果花青素形成機理研究中取得的新進展。
蘋果是我國栽培面積最大,、產(chǎn)量最多的水果,，也是世界上種植面積最大的栽培果樹之一。紅蘋果具有外觀鮮艷和營養(yǎng)豐富的雙重特點,，一直以來深受人們的喜愛,。紅蘋果呈現(xiàn)出的紅色是花青素（anthocyanin）的大量累積形成的，同時還富含許多對人體健康有益的原花青素（Proanthocyanidin,；PA）,。然而，紅蘋果花青素的合成途徑始終是現(xiàn)代研究的焦點,，而對原花青素合成途徑的研究甚少,。
中科院武漢植物園果樹分子育種課題組與美國伊利諾伊大學開展合作研究,，通過蘋果花青素還原酶（ANR）的轉(zhuǎn)基因試驗，發(fā)現(xiàn)ANR對植物花青苷,、黃酮醇等類黃酮物質(zhì)的合成具有調(diào)控作用,。
原花青素是水果中一種重要功能性成分，由花青素還原酶（ANR）催化合成,。該研究利用蘋果BAC文庫克隆了花青素還原酶基因（ANR）家族的兩個成員,，分別定位于第5、10號染色體,，發(fā)現(xiàn)ANR基因在煙草中過量表達不僅能夠抑制查爾酮異構(gòu)酶基因（CHI）和二氫黃酮醇4-還原酶基因（DFR）表達,，而且也影響黃酮醇合成酶基因（FLS）和無色花色素還原酶基因（LAR）的表達，最終表現(xiàn)為阻止花青苷的積累,、改變花器官的著色方式,。
研究同時還發(fā)現(xiàn)，蘋果MdANR基因在果實發(fā)育后期的非紅皮品種果皮中的表達水平高于紅皮品種,，揭示了ANR基因與花青苷代謝途徑中的CHI,、DFR等其他結(jié)構(gòu)基因存在協(xié)同作用，共同調(diào)控植物花青苷,、黃酮醇等類黃酮物質(zhì)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.
