Department of Plant Physiology, Warsaw University of Life Science-SGGW, Nowoursynowska 159, 02-776, Warsaw, Poland.
Planta. 2010 Nov;232(6):1397-407. doi: 10.1007/s00425-010-1262-2. Epub 2010 Sep 10.
The connection between classical phytohormone-ethylene and two signaling molecules, nitric oxide (NO) and hydrogen cyanide (HCN), was investigated in dormancy removal and germination "sensu stricto" of apple (Malus domestica Borkh.) embryos. Deep dormancy of apple embryos was removed by short-term (3-6 h) pre-treatment with NO or HCN. NO- or HCN-mediated stimulation of germination was associated with enhanced emission of ethylene by the embryos, coupled with transient increase in ROS concentration in embryos. Ethylene vapors stimulated germination of dormant apple embryos and eliminated morphological anomalies characteristic for young seedlings developed from dormant embryos. Inhibitors of ethylene receptors completely impeded beneficial effect of NO and HCN on embryo germination. NO- and HCN-induced ethylene emission by apple embryo was only slightly reduced by inhibitor of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase activity during first 4 days of germination. Short-term pre-treatment of the embryos with NO and HCN modified activity of both key enzymes of ethylene biosynthetic pathway: ACC synthase and ACC oxidase. Activity of ACC synthase declined during first 4 days of germination, while activity of ACC oxidase increased markedly at that time. Additional experiments point to non-enzymatic conversion of ACC to ethylene in the presence of ROS (H(2)O(2)). The results indicate that NO and HCN may alleviate dormancy of apple embryos "via" transient accumulation of ROS, leading to enhanced ethylene emission which is required to terminate germination "sensu stricto". Therefore, ethylene seems to be a trigger factor in control of apple embryo dormancy removal and germination.
经典植物激素乙烯与两种信号分子一氧化氮（NO）和氰化氢（HCN）之间的关系在苹果（Malus domestica Borkh.）胚胎休眠解除和萌发“本义”中进行了研究。苹果胚胎的深度休眠通过 NO 或 HCN 的短期（3-6 h）预处理来消除。NO 或 HCN 介导的萌发刺激与胚胎中乙烯的增强排放有关，同时胚胎中 ROS 浓度短暂增加。乙烯蒸气刺激休眠的苹果胚胎萌发，并消除了从休眠胚胎发育而来的幼苗的形态异常。乙烯受体抑制剂完全阻止了 NO 和 HCN 对胚胎萌发的有益影响。在萌发的前 4 天，1-氨基环丙烷-1-羧酸（ACC）氧化酶活性抑制剂仅略微减少了苹果胚胎中由 NO 和 HCN 诱导的乙烯排放。NO 和 HCN 对苹果胚胎中两种关键乙烯生物合成途径酶的活性进行了短期预处理：ACC 合酶和 ACC 氧化酶。在萌发的前 4 天，ACC 合酶的活性下降，而 ACC 氧化酶的活性在此时明显增加。进一步的实验表明，在 ROS（H2O2）存在下，ACC 可以非酶促转化为乙烯。研究结果表明，NO 和 HCN 可能通过 ROS 的短暂积累来减轻苹果胚胎的休眠，从而增强需要终止萌发“本义”的乙烯排放。因此，乙烯似乎是控制苹果胚胎休眠解除和萌发的触发因素。
