School of Life Sciences, University of Nevada, 4505 Maryland Parkway, Las Vegas, Las Vegas, NV, 89154-4004, USA.
BMC Plant Biol. 2024 Nov 18;24(1):1090. doi: 10.1186/s12870-024-05808-9.
Early seed germination in crops can confer a competitive advantage against weeds and reduce the time to maturation and harvest. WRKY transcription factors regulate many aspects of plant development including seed dormancy and germination. Both positive and negative regulators of seed germination have been reported in many plants such as rice and Arabidopsis. Using a transient expression system, we previously demonstrated that OsWRKY71 is a negative regulator of gibberellin (GA) signaling in aleurone cells and likely forms a "repressosome" complex with other transcriptional repressors. Hence, it has the potential to impact seed germination properties.
In this study, we demonstrate that OsWRKY71, a Group IIa WRKY gene, appeared at the same time as seed-bearing plants. Rice mutants lacking OsWRKY71 have seeds and embryos that germinate earlier than wildtype controls. In oswrky71 aleurone layers, α-amylase activity was hypersensitive to stimulation by GA and hyposensitive to inhibition by abscisic acid (ABA). Early germination in oswrky71 intact seeds was also hyposensitive to ABA. Transcriptomic profiling during embryo germination and early post-germination growth demonstrates that OsWRKY71 influences the expression of 9-17% of genes in dry and imbibing embryos. Compared to wildtype embryos, the mutant transcriptomes have large temporal shifts at 4, 8 and 12 h after imbibition (HAI). Importantly, many genes involved in the ABA-dependent inhibition of seed germination were downregulated in oswrky71-1. This mutant also displayed altered expression of multiple ABA receptors (OsPYLs/RCARs) that control ABA signaling and the VP1-SDR4-DOG1L branch of ABA signaling that promotes seed dormancy. Association studies reveal an OsWRKY71-containing quantitative trait locus involved in low-temperature seed germinability, qLTG-2. Indeed, oswrky71 seeds germinated early at 15 °C.
Rice Group-IIa WRKY transcription factor OsWRKY71 is a master regulator of germination that influences the expression of 9-17% of genes in dry and imbibing embryos. It is also most likely the primary candidate of low-temperature seed germinability QTL, qLTG-2. We propose that knockouts of OsWRKY71 can generate rice varieties with improved germination properties under normal or low-temperature conditions.
作物的早期种子萌发可以赋予其与杂草竞争的优势，并缩短成熟和收获的时间。WRKY 转录因子调节植物发育的许多方面，包括种子休眠和萌发。在许多植物中，如水稻和拟南芥，已经报道了种子萌发的正调控因子和负调控因子。我们之前使用瞬时表达系统证明，OsWRKY71 是糊粉细胞中赤霉素（GA）信号的负调控因子，可能与其他转录抑制剂形成“抑制复合物”。因此，它有可能影响种子萌发特性。
在这项研究中，我们证明了 OsWRKY71，一个 IIa 组 WRKY 基因，与带种子的植物同时出现。缺乏 OsWRKY71 的水稻突变体的种子和胚胎比野生型对照更早萌发。在 oswrky71 糊粉层中，α-淀粉酶活性对 GA 的刺激敏感，对 ABA 的抑制敏感。oswrky71 完整种子的早期萌发也对 ABA 不敏感。胚胎萌发和早期萌发后生长过程中的转录组谱分析表明，OsWRKY71 影响干种子和吸胀种子中 9-17%基因的表达。与野生型胚胎相比，突变体转录组在吸胀后 4、8 和 12 小时（HAI）有较大的时间变化。重要的是，许多参与 ABA 依赖的种子萌发抑制的基因在 oswrky71-1 中下调。该突变体还显示出多个 ABA 受体（OsPYLs/RCARs）的表达改变，这些受体控制 ABA 信号转导和促进种子休眠的 VP1-SDR4-DOG1L 分支的 ABA 信号转导。关联研究揭示了一个包含 OsWRKY71 的数量性状位点（QTL）参与低温种子发芽率，qLTG-2。事实上，oswrky71 种子在 15°C 时很早就萌发了。
水稻 IIa 组 WRKY 转录因子 OsWRKY71 是萌发的主要调节剂，影响干种子和吸胀种子中 9-17%基因的表达。它也很可能是低温种子发芽率 QTL，qLTG-2 的主要候选基因。我们提出，OsWRKY71 的敲除可以在正常或低温条件下产生具有改良萌发特性的水稻品种。
