Increasing planting density is a key strategy to enhance maize yields^1-3. An ideotype for dense planting requires a ‘smart canopy’ with leaf angles at different canopy layers differentially optimized to maximize light interception and photosynthesis^4-6, amongst other features. Here, we identified leaf angle architecture of smart canopy 1 (lac1), a natural mutant possessing upright upper leaves, less erect middle leaves and relatively flat lower leaves. lac1 has improved photosynthetic capacity and weakened shade-avoidance responses under dense planting. lac1 encodes a brassinosteroid C-22 hydroxylase that predominantly regulates upper leaf angle. Phytochrome A photoreceptors accumulate in shade and interact with the transcription factor RAVL1 to promote its degradation via the 26S proteasome, thereby attenuating RAVL1 activation of lac1 and reducing brassinosteroid levels. This ultimately decreases upper leaf angle in dense fields. Large-scale field trials demonstrate lac1 boosts maize yields under high densities. To quickly introduce lac1 into breeding germplasm, we transformed a haploid inducer and recovered homozygous lac1 edits from 20 diverse inbred lines. The tested doubled haploids uniformly acquired smart-canopy-like plant architecture. We provide an important target and an accelerated strategy for developing high-density-tolerant cultivars, with lac1 serving as a genetic chassis for further engineering of a smart canopy in maize.

增加种植密度是提高玉米产量的关键策略^1-3 。密集种植的理想型需要“智能冠层”，不同冠层层的叶角进行差异化优化，以最大限度地提高光拦截和光合作用^4-6等功能。在这里，我们确定了 smart canopy 1 ( lac1 )的叶角结构，这是一种自然突变体，具有直立的上部叶子、不太直立的中部叶子和相对平坦的下部叶子。 lac1在密植下提高了光合能力并减弱了避荫反应。 lac1编码油菜素类固醇 C-22 羟化酶，主要调节上叶角度。光敏色素 A 光感受器在阴凉处积聚，并与转录因子 RAVL1 相互作用，促进其通过 26S 蛋白酶体降解，从而减弱 RAVL1 对lac1的激活并降低油菜素类固醇水平。这最终会降低密集田地中的上叶角度。大规模田间试验表明， lac1在高密度下可提高玉米产量。为了快速将lac1引入育种种质，我们转化了单倍体诱导子并从 20 个不同的自交系​​中恢复了纯合lac1编辑。测试的双单倍体一致获得了智能冠层状植物结构。我们为开发高密度耐受品种提供了一个重要的目标和加速策略，其中lac1作为进一步工程玉米智能冠层的遗传底盘。