College of Horticulture, Qingdao Agricultural University, Qingdao 266109, China.
Qingdao Key Laboratory of Genetic Development and Breeding in Horticultural Plants, Qingdao 266109, China.
Tree Physiol. 2021 Jun 7;41(6):1065-1076. doi: 10.1093/treephys/tpaa162.
MdCoL, which encodes a putative 2OG-Fe(II) oxygenase, is a strong candidate gene for control of the columnar growth phenotype in apple. However, the mechanism by which MdCoL produces the columnar trait is unclear. Here, we show that MdCoL influences abscisic acid (ABA) biosynthesis through its interactions with the MdDREB2 transcription factor. Expression analyses and transgenic tobacco studies have confirmed that MdCoL is likely a candidate for control of the columnar phenotype. Furthermore, the ABA level in columnar apple trees is significantly higher than that in standard apple trees. A protein interaction experiment has showed that MdCoL interacts with MdDREB2. Transient expression and electrophoretic mobility shift assays have demonstrated that MdDREB2 binds directly to the DRE motif in the MdNCED6 and MdNCED9 (MdNCED6/9) gene promoters, thereby activating the transcription of these ABA biosynthesis genes. In addition, a higher ABA content has been detected following co-overexpression of MdCoL-MdDREB2 when compared with the overexpression of MdCoL or MdDREB2 alone. Taken together, our results indicate that an interaction between MdCoL and MdDREB2 promotes the expression of MdNCED6/9 and increases ABA levels, a phenomenon that may underlie the columnar growth phenotype in apple.
MdCoL 编码一个假定的 2OG-Fe(II) 加氧酶，是控制苹果柱状生长表型的候选基因。然而，MdCoL 产生柱状性状的机制尚不清楚。在这里，我们表明 MdCoL 通过与 MdDREB2 转录因子相互作用影响脱落酸（ABA）的生物合成。表达分析和转基因烟草研究证实，MdCoL 可能是控制柱状表型的候选基因。此外，柱状苹果树中的 ABA 水平明显高于标准苹果树。蛋白质相互作用实验表明 MdCoL 与 MdDREB2 相互作用。瞬时表达和电泳迁移率变动分析表明，MdDREB2 直接结合到 MdNCED6 和 MdNCED9（MdNCED6/9）基因启动子中的 DRE 基序，从而激活这些 ABA 生物合成基因的转录。此外，与单独过表达 MdCoL 或 MdDREB2 相比，共过表达 MdCoL-MdDREB2 时检测到更高的 ABA 含量。总之，我们的结果表明，MdCoL 和 MdDREB2 之间的相互作用促进了 MdNCED6/9 的表达并增加了 ABA 水平，这一现象可能是苹果柱状生长表型的基础。
