Over the past few decades, significant improvements in maize yield have been largely attributed to increased plant density of upright hybrid varieties rather than increased yield per plant. However, dense planting triggers shade avoidance responses (SARs) that optimize light absorption but impair plant vigor and performance, limiting yield improvement through increasing plant density. In this study, we demonstrated that high-density-induced leaf angle narrowing and stem/stalk elongation are largely dependent on phytochrome B (phyB1/B2), the primary photoreceptor responsible for perceiving red (R) and far-red (FR) light in maize. We found that maize phyB physically interacts with the LIGULELESS1 (LG1), a classical key regulator of leaf angle, to coordinately regulate plant architecture and density tolerance. The abundance of LG1 is significantly increased by phyB under high R:FR light (low density) but rapidly decreases under low R:FR light (high density), correlating with variations in leaf angle and plant height under various densities. In addition, we identified the homeobox transcription factor as a target co-repressed by both phyB and LG1 but rapidly induced by canopy shade. Genetic and cellular analyses showed that regulates plant architecture by controlling the elongation and division of ligular adaxial and abaxial cells. Taken together, these findings uncover the phyB-LG1- regulatory module as a key molecular mechanism governing plant architecture and density tolerance, providing potential genetic targets for breeding maize hybrid varieties suitable for high-density planting.

中文翻译：

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光敏色素 B 与 LIGULELESS1 相互作用来控制玉米的植物结构和密度耐受性


在过去的几十年里，玉米产量的显着提高主要归因于直立杂交品种的植株密度的增加，而不是单株产量的增加。然而，密集种植会引发避荫反应（SAR），从而优化光吸收，但会损害植物活力和性能，限制通过增加植物密度来提高产量。在这项研究中，我们证明高密度诱导的叶角变窄和茎/茎伸长在很大程度上取决于光敏色素 B (phyB1/B2)，光敏色素 B 是负责感知红光 (R) 和远红光 (FR) 的主要光感受器在玉米中。我们发现玉米 phyB 与 LIGULELESS1 (LG1)（叶角的经典关键调节因子）发生物理相互作用，以协调调节植物结构和密度耐受性。在高 R:FR 光（低密度）下，phyB 显着增加了 LG1 的丰度，但在低 R:FR 光（高密度）下，LG1 的丰度迅速下降，这与不同密度下叶角和株高的变化相关。此外，我们还发现同源盒转录因子是 phyB 和 LG1 共同抑制的靶标，但会被冠层遮荫快速诱导。遗传和细胞分析表明，它通过控制叶状近轴和远轴细胞的伸长和分裂来调节植物结构。总而言之，这些发现揭示了 phyB-LG1- 调控模块作为控制植物结构和密度耐受性的关键分子机制，为选育适合高密度种植的玉米杂交品种提供了潜在的遗传靶点。