Sagawa Janelle M, Stanley Lauren E, LaFountain Amy M, Frank Harry A, Liu Chang, Yuan Yao-Wu
Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, 06269, USA.
Department of Chemistry, University of Connecticut, Storrs, CT, 06269, USA.
New Phytol. 2016 Feb;209(3):1049-57. doi: 10.1111/nph.13647. Epub 2015 Sep 17.
Carotenoids are yellow, orange, and red pigments that contribute to the beautiful colors and nutritive value of many flowers and fruits. The structural genes in the highly conserved carotenoid biosynthetic pathway have been well characterized in multiple plant systems, but little is known about the transcription factors that control the expression of these structural genes. By analyzing a chemically induced mutant of Mimulus lewisii through bulk segregant analysis and transgenic experiments, we have identified an R2R3-MYB, Reduced Carotenoid Pigmentation 1 (RCP1), as the first transcription factor that positively regulates carotenoid biosynthesis during flower development. Loss-of-function mutations in RCP1 lead to down-regulation of all carotenoid biosynthetic genes and reduced carotenoid content in M. lewisii flowers, a phenotype recapitulated by RNA interference in the wild-type background. Overexpression of this gene in the rcp1 mutant background restores carotenoid production and, unexpectedly, results in simultaneous decrease of anthocyanin production in some transgenic lines by down-regulating the expression of an activator of anthocyanin biosynthesis. Identification of transcriptional regulators of carotenoid biosynthesis provides the 'toolbox' genes for understanding the molecular basis of flower color diversification in nature and for potential enhancement of carotenoid production in crop plants via genetic engineering.
类胡萝卜素是黄色、橙色和红色色素，它们赋予了许多花朵和果实美丽的颜色及营养价值。在多个植物系统中，高度保守的类胡萝卜素生物合成途径中的结构基因已得到充分表征，但对于控制这些结构基因表达的转录因子却知之甚少。通过对化学诱导的刘易斯猴面花突变体进行混合分组分析和转基因实验，我们鉴定出一个R2R3-MYB转录因子，即类胡萝卜素色素沉着减少1（RCP1），它是花发育过程中正向调控类胡萝卜素生物合成的首个转录因子。RCP1功能缺失突变导致刘易斯猴面花中所有类胡萝卜素生物合成基因下调，类胡萝卜素含量降低，这种表型在野生型背景下通过RNA干扰得以重现。在rcp1突变体背景中过表达该基因可恢复类胡萝卜素的合成，并且出乎意料的是，在一些转基因株系中，通过下调花青素生物合成激活因子的表达，导致花青素合成同时减少。类胡萝卜素生物合成转录调节因子的鉴定为理解自然界中花色多样化的分子基础以及通过基因工程潜在提高作物中类胡萝卜素产量提供了“工具箱”基因。
