MYB transcription factors (TFs) are involved in the regulation of flavonoid biosynthesis in both Chilean white strawberry (Fragaria chiloensis) and commercial strawberry (Fragaria × ananassa). There is evidence that MYB1 TF repress anthocyanin biosynthesis, but would also be participating in the regulation of the proanthocyanidin (PA) polymer synthesis, either in the activation or repression of the expression of PA-related genes. We investigated the role of the MYB1 TF in the regulation of the PA-associated structural gene leucoanthocyanidin reductase (LAR). The promoter regions of LAR were isolated from F. chiloensis and F. × ananassa genomes and named as pFcLAR and pFaLAR, respectively. Promoter analysis revealed several putative binding sites for MYBs and bHLH TFs. Then, dual luciferase assays were conducted to investigate whether MYB1 can act as a transactivator of LAR promoters in both species. In the long version of LAR promoters of both species (1381 bp upstream of ATG), the addition of MYB1 to the MYB10-bHLH3 complex repressed the activation. However, when using the medium version of the pFcLAR (815 bp upstream of ATG), MYB1 alone significantly activated the promoter, and no repression was observed when MYB1 was added to the MYB10-bHLH3 complex in the short pFa/FcLAR promoters (316 bp upstream of ATG). We propose that the FcMYB1 TF could regulate PA biosynthesis, and that its role, as either a repressor or activator, is dependent of other partners and the DNA sequence context of the promoter regions.

MYB 转录因子 (TF) 参与智利白草莓 ( Fragaria chiloensis ) 和商业草莓 ( Fragaria × ananassa ) 中类黄酮生物合成的调节。有证据表明 MYB1 TF 抑制花青素生物合成，但也参与调节原花青素 (PA) 聚合物合成，激活或抑制 PA 相关基因的表达。我们研究了 MYB1 TF 在 PA 相关结构基因无色花青素还原酶 ( LAR ) 的调节中的作用。LAR的启动子区从F. chiloensis和F. . × ananassa基因组，分别命名为 pFcLAR 和 pFaLAR。启动子分析揭示了 MYB 和 bHLH TF 的几个假定结合位点。然后，进行双荧光素酶测定以研究 MYB1 是否可以作为两个物种中LAR启动子的反式激活因子。在两个物种的长版本LAR启动子（ATG 上游 1381 bp）中，将 MYB1 添加到 MYB10-bHLH3 复合物中会抑制激活。然而，当使用中等版本的pFcLAR（ATG上游815 bp）时，单独的MYB1显着激活启动子，并且当将MYB1添加到短pFa/FcLAR启动子（316 bp）中的MYB10-bHLH3复合物中时，没有观察到抑制。 ATG 上游）。我们认为 FcMYB1 TF 可以调节 PA 生物合成，并且其作为抑制子或激活子的作用取决于其他伙伴和启动子区域的 DNA 序列背景。