Darbani Behrooz, Noeparvar Shahin, Borg Søren
Department of Molecular Biology and Genetics, Research Centre Flakkebjerg, Aarhus University, Slagelse, Denmark.
Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg, Denmark.
PLoS One. 2015 Nov 4;10(11):e0141398. doi: 10.1371/journal.pone.0141398. eCollection 2015.
In addition to the micronutrient inadequacy of staple crops for optimal human nutrition, a global downtrend in crop-quality has emerged from intensive breeding for yield. This trend will be aggravated by elevated levels of the greenhouse gas carbon dioxide. Therefore, crop biofortification is inevitable to ensure a sustainable supply of minerals to the large part of human population who is dietary dependent on staple crops. This requires a thorough understanding of plant-mineral interactions due to the complexity of mineral homeostasis. Employing RNA sequencing, we here communicate transfer cell specific effects of excess iron and zinc during grain filling in our model crop plant barley. Responding to alterations in mineral contents, we found a long range of different genes and transcripts. Among them, it is worth to highlight the auxin and ethylene signaling factors Arfs, Abcbs, Cand1, Hps4, Hac1, Ecr1, and Ctr1, diurnal fluctuation components Sdg2, Imb1, Lip1, and PhyC, retroelements, sulfur homeostasis components Amp1, Hmt3, Eil3, and Vip1, mineral trafficking components Med16, Cnnm4, Aha2, Clpc1, and Pcbps, and vacuole organization factors Ymr155W, RabG3F, Vps4, and Cbl3. Our analysis introduces new interactors and signifies a broad spectrum of regulatory levels from chromatin remodeling to intracellular protein sorting mechanisms active in the plant mineral homeostasis. The results highlight the importance of storage proteins in metal ion toxicity-resistance and chelation. Interestingly, the protein sorting and recycling factors Exoc7, Cdc1, Sec23A, and Rab11A contributed to the response as well as the polar distributors of metal-transporters ensuring the directional flow of minerals. Alternative isoform switching was found important for plant adaptation and occurred among transcripts coding for identical proteins as well as transcripts coding for protein isoforms. We also identified differences in the alternative-isoform preference between the treatments, indicating metal-affinity shifts among isoforms of metal transporters. Most important, we found the zinc treatment to impair both photosynthesis and respiration. A wide range of transcriptional changes including stress-related genes and negative feedback loops emphasize the importance to withhold mineral contents below certain cellular levels which otherwise might lead to agronomical impeding side-effects. By illustrating new mechanisms, genes, and transcripts, this report provides a solid platform towards understanding the complex network of plant mineral homeostasis.
除了主要作物的微量营养素不足以实现最佳人类营养外，由于为提高产量而进行的密集育种，全球作物质量出现了下降趋势。这种趋势将因温室气体二氧化碳水平的升高而加剧。因此，作物生物强化对于确保向大部分依赖主食的人群可持续供应矿物质是不可避免的。由于矿物质稳态的复杂性，这需要深入了解植物与矿物质的相互作用。利用RNA测序技术，我们在此阐述了在模式作物大麦灌浆期过量铁和锌对传递细胞的特定影响。针对矿物质含量的变化，我们发现了一系列不同的基因和转录本。其中，值得强调的是生长素和乙烯信号因子Arfs、Abcbs、Cand1、Hps4、Hac1、Ecr1和Ctr1，昼夜波动成分Sdg2、Imb1、Lip1和PhyC，反转录元件，硫稳态成分Amp1、Hmt3、Eil3和Vip1，矿物质运输成分Med16、Cnnm4、Aha2、Clpc1和Pcbps，以及液泡组织因子Ymr155W、RabG3F、Vps4和Cbl3。我们的分析引入了新的相互作用因子，并表明了从染色质重塑到植物矿物质稳态中活跃的细胞内蛋白质分选机制等广泛的调控水平。结果突出了储存蛋白在金属离子毒性抗性和螯合中的重要性。有趣的是，蛋白质分选和循环因子Exoc7、Cdc1、Sec23A和Rab11A以及金属转运蛋白的极性分布因子对这种反应也有贡献，确保了矿物质的定向流动。发现可变异构体切换对植物适应很重要，并且发生在编码相同蛋白质以及编码蛋白质异构体的转录本之间。我们还确定了处理之间可变异构体偏好的差异，表明金属转运蛋白异构体之间的金属亲和力发生了变化。最重要的是，我们发现锌处理会损害光合作用和呼吸作用。包括应激相关基因和负反馈回路在内的广泛转录变化强调了将矿物质含量控制在特定细胞水平以下的重要性，否则可能会导致农业上的不良副作用。通过阐明新的机制、基因和转录本，本报告为理解植物矿物质稳态的复杂网络提供了一个坚实的平台。
