Maia Julio, Dekkers Bas J W, Dolle Miranda J, Ligterink Wilco, Hilhorst Henk W M
Wageningen Seed Lab, Laboratory of Plant Physiology, Wageningen University, Wageningen, 6708 PB, the Netherlands.
New Phytol. 2014 Jul;203(1):81-93. doi: 10.1111/nph.12785. Epub 2014 Apr 3.
During germination, orthodox seeds lose their desiccation tolerance (DT) and become sensitive to extreme drying. Yet, DT can be rescued, in a well-defined developmental window, by the application of a mild osmotic stress before dehydration. A role for abscisic acid (ABA) has been implicated in this stress response and in DT re-establishment. However, the path from the sensing of an osmotic cue and its signaling to DT re-establishment is still largely unknown. Analyses of DT, ABA sensitivity, ABA content and gene expression were performed in desiccation-sensitive (DS) and desiccation-tolerant Arabidopsis thaliana seeds. Furthermore, loss and re-establishment of DT in germinated Arabidopsis seeds was studied in ABA-deficient and ABA-insensitive mutants. We demonstrate that the developmental window in which DT can be re-established correlates strongly with the window in which ABA sensitivity is still present. Using ABA biosynthesis and signaling mutants, we show that this hormone plays a key role in DT re-establishment. Surprisingly, re-establishment of DT depends on the modulation of ABA sensitivity rather than enhanced ABA content. In addition, the evaluation of several ABA-insensitive mutants, which can still produce normal desiccation-tolerant seeds, but are impaired in the re-establishment of DT, shows that the acquisition of DT during seed development is genetically different from its re-establishment during germination.
在萌发过程中，传统种子会丧失其脱水耐受性（DT），并对极端干燥变得敏感。然而，在一个明确界定的发育窗口内，通过在脱水前施加轻度渗透胁迫，可以恢复DT。脱落酸（ABA）在这种胁迫反应和DT重建中被认为发挥了作用。然而，从感知渗透信号及其信号传导到DT重建的途径仍 largely未知。对脱水敏感（DS）和脱水耐受的拟南芥种子进行了DT、ABA敏感性、ABA含量和基因表达的分析。此外，在ABA缺陷和ABA不敏感的突变体中研究了萌发的拟南芥种子中DT的丧失和重建。我们证明，DT可以重建的发育窗口与ABA敏感性仍然存在的窗口密切相关。使用ABA生物合成和信号突变体，我们表明这种激素在DT重建中起关键作用。令人惊讶的是，DT的重建取决于ABA敏感性的调节，而不是ABA含量的增加。此外，对几个ABA不敏感突变体的评估表明，这些突变体仍能产生正常的脱水耐受种子，但在DT重建方面受损，这表明种子发育过程中DT的获得在遗传上与其萌发过程中的重建不同。
