Santopolo Silvia, Boccaccini Alessandra, Lorrai Riccardo, Ruta Veronica, Capauto Davide, Minutello Emanuele, Serino Giovanna, Costantino Paolo, Vittorioso Paola
BMC Plant Biol. 2015 Mar 4;15:72. doi: 10.1186/s12870-015-0453-1.
The transcription factor DOF AFFECTING GERMINATION1 (DAG1) is a repressor of the light-mediated seed germination process. DAG1 acts downstream PHYTOCHROME INTERACTING FACTOR3-LIKE 5 (PIL5), the master repressor, and negatively regulates gibberellin biosynthesis by directly repressing the biosynthetic gene AtGA3ox1. The Dof protein DOF AFFECTING GERMINATION (DAG2) shares a high degree of aminoacidic identity with DAG1. While DAG1 inactivation considerably increases the germination capability of seeds, the dag2 mutant has seeds with a germination potential substantially lower than the wild-type, indicating that these factors may play opposite roles in seed germination.
We show here that DAG2 expression is positively regulated by environmental factors triggering germination, whereas its expression is repressed by PIL5 and DAG1; by Chromatin Immuno Precipitation (ChIP) analysis we prove that DAG1 directly regulates DAG2. In addition, we show that Red light significantly reduces germination of dag2 mutant seeds.
In agreement with the seed germination phenotype of the dag2 mutant previously published, the present data prove that DAG2 is a positive regulator of the light-mediated seed germination process, and particularly reveal that this protein plays its main role downstream of PIL5 and DAG1 in the phytochrome B (phyB)-mediated pathway.
转录因子DOF影响萌发1（DAG1）是光介导种子萌发过程的抑制因子。DAG1在主要抑制因子光敏色素相互作用因子3样5（PIL5）的下游起作用，并通过直接抑制生物合成基因AtGA3ox1来负调控赤霉素生物合成。Dof蛋白DOF影响萌发（DAG2）与DAG1具有高度的氨基酸序列同一性。虽然DAG1失活显著提高了种子的萌发能力，但dag2突变体种子的萌发潜力明显低于野生型，这表明这些因子在种子萌发中可能发挥相反的作用。
我们在此表明，DAG2的表达受触发萌发的环境因子正调控，而其表达受PIL5和DAG1抑制；通过染色质免疫沉淀（ChIP）分析，我们证明DAG1直接调控DAG2。此外，我们表明红光显著降低dag2突变体种子的萌发率。
与先前发表的dag2突变体的种子萌发表型一致，目前的数据证明DAG2是光介导种子萌发过程中的正调控因子，尤其揭示了该蛋白在光敏色素B（phyB）介导的途径中在PIL5和DAG1的下游发挥主要作用。
