Phytohormone brassinosteroids (BRs) are essential for plant growth and development, but the mechanisms of BR-mediated pollen development remain largely unknown. In this study, we show that pollen viability, pollen germination and seed number decreased in the BR-deficient mutant d^im , which has a lesion in the BR biosynthetic gene DWARF (DWF), and in the bzr1 mutant, which is deficient in BR signaling regulator BRASSINAZOLE RESISTANT 1 (BZR1), compared with those in wild-type plants, whereas plants overexpressing DWF or BZR1 exhibited the opposite effects. Loss or gain of function in the DWF or BZR1 genes altered the timing of reactive oxygen species (ROS) production and programmed cell death (PCD) in tapetal cells, resulting in delayed or premature tapetal degeneration, respectively. Further analysis revealed that BZR1 could directly bind to the promoter of RESPIRATORY BURST OXIDASE HOMOLOG 1 (RBOH1), and that RBOH1-mediated ROS promote pollen and seed development by triggering PCD and tapetal cell degradation. In contrast, the suppression of RBOH1 compromised BR signaling-mediated ROS production and pollen development. These findings provide strong evidence that BZR1-dependent ROS production plays a critical role in the BR-mediated regulation of tapetal cell degeneration and pollen development in Solanum lycopersicum (tomato) plants.

中文翻译：

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油菜素类固醇介导的活性氧对于番茄的绒毡层降解和花粉育性至关重要。

植物激素油菜素类固醇（BRs）对于植物的生长和发育至关重要，但是BR介导的花粉发育的机制仍然未知。在这项研究中，我们表明，在BR生物合成基因DWARF（DWF）和bzr1突变体（其缺乏）中，在BR缺陷突变体d ^ im中存在花粉活力，花粉萌发和种子数目减少。 BR信号调节剂BRASSINAZOLE RESISTANT 1（BZR1）与野生型植物相比，而过表达DWF或BZR1的植物表现出相反的作用。DWF或BZR1基因的功能丧失或获得改变了绒毛细胞中活性氧（ROS）产生和程序性细胞死亡（PCD）的时间，分别导致延迟或过早的绒毛变性。进一步的分析表明，BZR1可以直接与呼吸爆发性氧化酶同系物1（RBOH1）的启动子结合，而RBOH1介导的ROS通过触发PCD和绒毛细胞降解来促进花粉和种子发育。相反，抑制RBOH1损害了BR信号介导的ROS产生和花粉发育。这些发现提供了有力的证据，证明依赖BZR1的ROS的产生在BR介导的番茄茄中绒毛细胞变性和花粉发育的调节中起着关键作用。