Red fruit peel is an attractive target for pineapple breeding. Various pineapple accessions with distinct red coloration patterns exist, however, the precise molecular mechanism accounting for these differences remains unknown, which hinders the pineapple breeding process from combining high fruit quality with red peel. In this study, we characterized a transcription factor, AcMYB266, which is preferentially expressed in pineapple peel and positively regulates anthocyanin accumulation. Transgenic pineapple, Arabidopsis, and tobacco plants overexpressing AcMYB266 exhibited significant anthocyanin accumulation; Conversely, transient silencing of this gene led to decreased anthocyanin accumulation in pineapple red bracts. In-depth analysis indicated that variations of AcMYB266 sequences in promoter instead of protein-coding region seem to contribute to different red coloration patterns in peels of three representative pineapple varieties. In addition, we found that AcMYB266 was located in a four MYB gene cluster exclusive-conserved to Ananas species. Of this cluster, each was proved to regulate anthocyanin synthesis in different pineapple tissues, illustrating an interesting case of gene subfunctionalization after tandem duplication. In summary, we have characterized AcMYB266 as a key regulator of pineapple red fruit peel and identified a MYB cluster, members of which were subfunctionalized to specifically regulate the red coloration of different pineapple tissues. The present study will assist in establishing a theoretical mechanism for pineapple breeding for red fruit peel and provide an interesting case for the investigation of gene subfunctionalization in plants.

中文翻译：

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AcMYB266，菠萝皮红色的关键调节因子：串联重复基因亚功能化的一个案例

红色果皮是菠萝育种的一个有吸引力的目标。存在各种具有明显红色图案的菠萝种质，然而，解释这些差异的精确分子机制仍然未知，这阻碍了菠萝育种过程将高果实品质与红色果皮相结合。在这项研究中，我们鉴定了一种转录因子 AcMYB266，它优先在菠萝皮中表达，并正向调节花青素的积累。过表达 AcMYB266 的转基因菠萝、拟南芥和烟草植物表现出显着的花青素积累；相反，该基因的短暂沉默导致菠萝红苞片中花青素的积累减少。深入分析表明，AcMYB266 启动子序列（而不是蛋白质编码区）的变异似乎导致了三个代表性菠萝品种果皮不同的红色着色模式。此外，我们发现AcMYB266位于凤梨属物种独有保守的四个MYB基因簇中。该簇中的每一个都被证明可以调节不同菠萝组织中花青素的合成，说明了串联复制后基因亚功能化的有趣案例。总之，我们将 AcMYB266 定性为菠萝红色果皮的关键调节因子，并鉴定了 MYB 簇，其成员被亚功能化以特异性调节不同菠萝组织的红色着色。本研究将有助于建立菠萝红色果皮育种的理论机制，并为植物基因亚功能化的研究提供一个有趣的案例。