Department of Life Science, Hanyang University, Seoul 04763, Republic of Korea.
Research Institute for Convergence of Basic Science, Hanyang University, Seoul 04763, Republic of Korea.
Plant Cell. 2024 Sep 3;36(9):3654-3673. doi: 10.1093/plcell/koae172.
Anthocyanins play critical roles in protecting plant tissues against diverse stresses. The complicated regulatory networks induced by various environmental factors modulate the homeostatic level of anthocyanins. Here, we show that anthocyanin accumulation is induced by brassinosteroids (BRs) in Arabidopsis (Arabidopsis thaliana) shoots and shed light on the underlying regulatory mechanism. We observed that anthocyanin levels are altered considerably in BR-related mutants, and BRs induce anthocyanin accumulation by upregulating the expression of anthocyanin biosynthetic genes. Our genetic analysis indicated that BRASSINAZOLE RESISTANT 1 (BZR1) and PRODUCTION OF ANTHOCYANIN PIGMENT 1 (PAP1) are essential for BR-induced anthocyanin accumulation. The BR-responsive transcription factor BZR1 directly binds to the PAP1 promoter, regulating its expression. In addition, we found that intense anthocyanin accumulation caused by the pap1-D-dominant mutation is significantly reduced in BR mutants, implying that BR activity is required for PAP1 function after PAP1 transcription. Moreover, we demonstrated that BZR1 physically interacts with PAP1 to cooperatively regulate the expression of PAP1-target genes, such as TRANSPARENT TESTA 8, DIHYDROFLAVONOL 4-REDUCTASE, and LEUKOANTHOCYANIDIN DIOXYGENASE. Our findings indicate that BZR1 functions as an integral component of the PAP1-containing transcription factor complex, contributing to increased anthocyanin biosynthesis. Notably, we also show that functional interaction of BZR1 with PAP1 is required for anthocyanin accumulation induced by low nitrogen stress. Taken together, our results demonstrate that BR-regulated BZR1 promotes anthocyanin biosynthesis through cooperative interaction with PAP1 of the MBW complex.
花青素有保护植物组织免受各种胁迫的关键作用。各种环境因素诱导的复杂调控网络调节花青苷的内稳态水平。在这里，我们表明，在拟南芥（Arabidopsis thaliana）茎中，油菜素内酯（BRs）诱导花青苷积累，并揭示了其潜在的调控机制。我们观察到，BR 相关突变体中花青苷水平发生了显著变化，BRs 通过上调花青苷生物合成基因的表达诱导花青苷积累。我们的遗传分析表明，BRASSINAZOLE RESISTANT 1（BZR1）和 PRODUCTION OF ANTHOCYANIN PIGMENT 1（PAP1）是 BR 诱导花青苷积累所必需的。BR 响应转录因子 BZR1 直接结合 PAP1 启动子，调节其表达。此外，我们发现，pap1-D 显性突变引起的强烈花青苷积累在 BR 突变体中显著减少，这表明 BR 活性在 PAP1 转录后对 PAP1 功能是必需的。此外，我们证明 BZR1 与 PAP1 物理相互作用，共同调节 PAP1 靶基因的表达，如 TRANSPARENT TESTA 8、DIHYDROFLAVONOL 4-REDUCTASE 和 LEUKOANTHOCYANIDIN DIOXYGENASE。我们的研究结果表明，BZR1 作为包含 PAP1 的转录因子复合物的一个组成部分发挥作用，有助于增加花青苷生物合成。值得注意的是，我们还表明，BZR1 与 PAP1 的功能相互作用是低氮胁迫诱导花青苷积累所必需的。总之，我们的研究结果表明，BR 调节的 BZR1 通过与 PAP1 的协同相互作用促进花青苷生物合成。
