Brassinosteroids (BRs) are a class of plant-specific steroid hormones and play an essential role in plant growth and development. The DWARF4 (DWF4) gene encodes a C-22 hydroxylase, which is a rate-limiting enzyme in BR biosynthesis pathway. Here, the DWF4 (ZmDWF4) in maize (Zea mays L.), the ortholog of Arabidopsis DWF4 (CYP90B1), was transformed into elite inbred Q319 and driven maize ubiquitin promoter. In transgenic lines, the level of the endogenous BR precursor canosterone (CS) was significantly enhanced. ZmDWF4 overexpression greatly improved grain yield per ear from 28.3 to 33.5% in transgenic lines compared with that in non-transgenic Q319 plants. Moreover, ZmDWF4 overexpression significantly enhanced heterosis of combinations by increasing both seed number and seed weight up to 20.4% in transgenic hybrids. Further analysis revealed that ZmDWF4 overexpression significantly improved several agronomic traits and leaf photosynthetic ability in transgenic lines. Finally, RNA-seq analysis suggested that overexpressing ZmDWF4 improved cell growth, cell division, and nutrient assimilation in transgenic kernels. Altogether, our results demonstrate that manipulating BR level by overexpressing ZmDWF4 effectively improves maize agronomic traits, and thus, provides a useful biotechnological strategy for the genetic improvement and further commercially favorable maize breeding.

油菜素类固醇（BRs）是一类植物特定的类固醇激素，在植物的生长发育中起着至关重要的作用。所述DWARF4（DWF4）基因编码C-22羟化酶，这是BR生物合成途径中的限速酶。这里，DWF4（ZmDWF4）在玉米（玉蜀黍L.），的直向同源物拟南芥DWF4（CYP90B1），转化到优良近交Q319和从动玉米泛素启动子。在转基因品系中，内源性BR前体睾酮（CS）的水平显着提高。ZmDWF4与非转基因Q319植物相比，过表达大大提高了转基因品系的每穗谷物产量，从28.3％提高到33.5％。此外，ZmDWF4的过表达通过增加转基因杂种中的种子数量和种子重量达20.4％，显着增强了组合的杂种优势。进一步的分析表明，ZmDWF4的过表达显着改善了转基因品系的若干农艺性状和叶片的光合能力。最后，RNA-seq分析表明，过表达ZmDWF4可以改善转基因谷粒中的细胞生长，细胞分裂和营养同化。总之，我们的结果表明，通过过度表达ZmDWF4来调节BR水平。 有效地改善了玉米的农艺性状，从而为遗传改良和进一步的商业上有利的玉米育种提供了有用的生物技术策略。