A novel R2R3-MYB transcription factor regulates light-mediated floral and vegetative anthocyanin pigmentation patterns in Lilium regale
A novel R2R3-MYB transcription factor regulates light-mediated floral and vegetative anthocyanin pigmentation patterns in Lilium regale
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DOI：
10.1007/s11032-015-0426-y
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发表时间：
2016-01-01
影响因子：
3.1
通讯作者：
Yamagishi, Masumi
中科院分区：
文献类型：
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作者：
Yamagishi, Masumi
被子植物花的颜色模式是由色素在空间和时间上的限制沉积而产生的。许多百合属植物在整个花被片上都表现出花青素的着色，这受MYB12/碱性螺旋-环-螺旋2(BHLH2)转录因子复合体的调控。然而，在百合中，色素的沉积仅限于花蕾、叶和苞片的光照表面。通过研究帝王乳杆菌独特的颜色模式是如何调控的，鉴定和分离了一个新的R2R3-MYB基因，LrMYB15。在烟草的稳定和瞬时转化试验中，LrMYB15促进了花青素生物合成基因的转录，表明它参与了花青素的正向调控。在龙舌兰中，花青素生物合成基因和LrMYB15在积累花青素的外部花被片、叶片和苞片中表达。相反，花青素生物合成的另一个调控基因LrbHLH2在所有器官中都有转录，与花青素的积累无关。这些结果表明，LrMYB15主要决定了龙须草独特的花色苷颜色模式。此外，LrMYB15基因的转录在植物处于遮荫条件下以及花蕾褪色时完全停止，表明该基因的转录受光控制。R2R3-MYB基因调控光诱导花瓣表面花青素的积累，已在真叶树中分离出来。这些结果表明，R2R3-MYB基因具有相似(但不完全相同)的功能，在单子叶植物和真子叶植物之间是保守的，转录调控是在多种被子植物的花中产生限制性色素沉积的主要机制。
Color patterns in angiosperm flowers are produced by spatially and temporally restricted deposition of pigments. Many Lilium species show anthocyanin pigmentation of the whole tepal, which is regulated by the MYB12/basic helix-loop-helix 2 (bHLH2) transcription factor complex. However, in Lilium regale pigment deposition is restricted to light-exposed surfaces of the flower buds, leaves, and bracts. Investigation of how the unique color patterns of L. regale are regulated led to the identification and isolation of a novel R2R3-MYB gene, LrMYB15. In stable and transient transformation assays in tobacco, LrMYB15 stimulated transcription of anthocyanin biosynthesis genes, indicating that it is involved in the positive regulation of anthocyanins. In L. regale, anthocyanin biosynthesis genes and LrMYB15 were expressed in the outer tepals, leaves, and bracts that accumulated anthocyanin pigments. In contrast, LrbHLH2, another regulatory gene for anthocyanin biosynthesis, was transcribed in all organs irrespective of anthocyanin accumulation. These results indicate that LrMYB15 principally determines the unique anthocyanin color patterns of L. regale. In addition, LrMYB15 transcription ceased completely when plants were kept in shaded conditions and the colors of the flower buds faded, indicating that transcription of this gene is under the control of light. R2R3-MYB genes that regulate light-induced anthocyanin accumulation on exposed petal surfaces have been isolated in eudicots. The results here indicate that R2R3-MYB genes exhibiting similar (but not identical) functions are conserved between monocots and eudicots and that transcriptional regulation is a major mechanism for generating restricted pigment deposition in the flowers of a wide range of angiosperm species.