Reichler Stuart A, Torres Jonathan, Rivera Amy L, Cintolesi Viviana A, Clark Greg, Roux Stanley J
University of Texas at Austin, Section of Molecular Cell and Developmental Biology, 1 University Station, A6700 Austin, TX 78712, USA.
J Exp Bot. 2009;60(7):2129-38. doi: 10.1093/jxb/erp091. Epub 2009 Apr 10.
Plant and animal cells release or secrete ATP by various mechanisms, and this activity allows extracellular ATP to serve as a signalling molecule. Recent reports suggest that extracellular ATP induces plant responses ranging from increased cytosolic calcium to changes in auxin transport, xenobiotic resistance, pollen germination, and growth. Although calcium has been identified as a secondary messenger for the extracellular ATP signal, other parts of this signal transduction chain remain unknown. Increasing the extracellular concentration of ATPgammaS, a poorly-hydrolysable ATP analogue, inhibited both pollen germination and pollen tube elongation, while the addition of AMPS had no effect. Because pollen tube elongation is also sensitive to nitric oxide, this raised the possibility that a connection exists between the two pathways. Four approaches were used to test whether the germination and growth effects of extracellular ATPgammaS were transduced via nitric oxide. The results showed that increases in extracellular ATPgammaS induced increases in cellular nitric oxide, chemical agonists of the nitric oxide signalling pathway lowered the threshold of extracellular ATPgammaS that inhibits pollen germination, an antagonist of guanylate cyclase, which can inhibit some nitric oxide signalling pathways, blocked the ATPgammaS-induced inhibition of both pollen germination and pollen tube elongation, and the effects of applied ATPgammaS were blocked in nia1nia2 mutants, which have diminished NO production. The concurrence of these four data sets support the conclusion that the suppression of pollen germination and pollen tube elongation by extracellular nucleotides is mediated in part via the nitric oxide signalling pathway.
植物和动物细胞通过多种机制释放或分泌ATP，这种活性使得细胞外ATP能够作为一种信号分子。最近的报道表明，细胞外ATP可诱导植物产生多种反应，从胞质钙浓度升高到生长素运输、异生物质抗性、花粉萌发和生长的变化。尽管钙已被确定为细胞外ATP信号的第二信使，但该信号转导链的其他部分仍不清楚。增加难以水解的ATP类似物ATPγS的细胞外浓度，会抑制花粉萌发和花粉管伸长，而添加AMPS则没有影响。由于花粉管伸长对一氧化氮也敏感，这就增加了两条途径之间存在联系的可能性。采用了四种方法来测试细胞外ATPγS对萌发和生长的影响是否通过一氧化氮进行转导。结果表明，细胞外ATPγS的增加会诱导细胞内一氧化氮增加，一氧化氮信号通路的化学激动剂降低了抑制花粉萌发的细胞外ATPγS阈值，一种可抑制某些一氧化氮信号通路的鸟苷酸环化酶拮抗剂，阻断了ATPγS诱导的花粉萌发和花粉管伸长的抑制作用，并且在nia1nia2突变体中，施加的ATPγS的作用被阻断，该突变体的一氧化氮产生减少。这四组数据的一致性支持了这样的结论，即细胞外核苷酸对花粉萌发和花粉管伸长的抑制作用部分是通过一氧化氮信号通路介导的。
