The University of Texas at Austin, 1 University Station A6700, Austin, Texas 78712, USA.
Am J Bot. 2013 Jan;100(1):161-74. doi: 10.3732/ajb.1200292. Epub 2012 Oct 9.
Gravity regulates the magnitude and direction of a trans-cell calcium current in germinating spores of Ceratopteris richardii. Blocking this current with nifedipine blocks the spore's downward polarity alignment, a polarization that is fixed by gravity ∼10 h after light induces the spores to germinate. RNA-seq analysis at 10 h was used to identify genes potentially important for the gravity response. The data set will be valuable for other developmental and phylogenetic studies.
De novo Newbler assembly of 958 527 reads from Roche 454 sequencing was executed. The sequences were identified and analyzed using in silico methods. The roles of endomembrane Ca(2+)-ATPase pumps and apyrases in the gravity response were further tested using pharmacological agents.
Transcripts related to calcium signaling and ethylene biosynthesis were identified as notable constituents of the transcriptome. Inhibiting the activity of endomembrane Ca(2+)-ATPase pumps with 2,5-di-(t-butyl)-1,4-hydroquinone diminished the trans-cell current, but increased the orientation of the polar axis to gravity. The effects of applied nucleotides and purinoceptor antagonists gave novel evidence implicating extracellular nucleotides as regulators of the gravity response in these fern spores.
In addition to revealing general features of the transcriptome of germinating spores, the results highlight a number of calcium-responsive and light-receptive transcripts. Pharmacologic assays indicate endomembrane Ca(2+)-ATPases and extracellular nucleotides may play regulatory roles in the gravity response of Ceratopteris spores.
重力调节拟南芥花粉粒中跨细胞钙离子流的大小和方向。用硝苯地平阻断该电流会阻止花粉的向下极性排列，这种极性在光照诱导花粉萌发约 10 小时后被重力固定。在 10 小时时进行 RNA-seq 分析，以鉴定对重力反应可能重要的基因。该数据集将对其他发育和系统发育研究具有重要价值。
对罗氏 454 测序的 958527 条reads 进行从头从头新布勒组装。使用计算机方法鉴定和分析这些序列。使用药理学试剂进一步测试内质网膜 Ca(2+)-ATP 酶泵和apyrases 在重力反应中的作用。
鉴定出与钙信号转导和乙烯生物合成相关的转录本作为转录组的显著组成部分。用 2,5-二-(叔丁基)-1,4-对苯二酚抑制内质网膜 Ca(2+)-ATP 酶泵的活性，减少跨细胞电流，但增加极性轴对重力的取向。施加核苷酸和嘌呤受体拮抗剂的效果提供了新的证据，表明细胞外核苷酸是这些蕨类植物花粉重力反应的调节剂。
除了揭示萌发花粉粒转录组的一般特征外，结果还突出了许多钙反应性和光受体转录本。药理测定表明，内质网膜 Ca(2+)-ATP 酶和细胞外核苷酸可能在拟南芥孢子的重力反应中发挥调节作用。
