Department of Biology, Faculty of Sciences, Golestan University, Gorgan, Iran.
Department of Statistics, Faculty of Sciences, Gorgan, Iran.
J Plant Physiol. 2019 Sep;240:153013. doi: 10.1016/j.jplph.2019.153013. Epub 2019 Jul 24.
The HCN-induced seed dormancy release necessitates alterations in reactive oxygen species (ROS) metabolism and radicle cell wall loosening. Little is known about the interaction of ROS metabolism with cell wall hydrolytic enzymes during HCN-induced seed dormancy release. Thus dormant walnut (Juglans regia L.) kernels were exposed to HCN (4 h) and studied for redox metabolism and cell wall-modifying enzymes during 10 days of incubation (DI) i.e. before radicle emergence. HCN increased ROS especially in the embryonic axes (EAs) but decreased ROS-generating NADPH oxidase and ROS scavenging superoxide dismutase (SOD) and peroxidase (POX) with no effects on catalase (CAT), ascorbate peroxidase (APX) and cell wall-modifying enzymes activities in short term up to 2 DI. In long term roughly from 4 DI onwards, HCN-exposed EA displayed greater superoxide anions and enhanced activities of POX, APX, NADPH oxidase, cell wall peroxidase (CW-POX), β- 1, 4-D glucanase, mannanase, polygacturonase and xylanase. Meanwhile HCN increased greater expression of POX and mannanase isoforms as revealed by in-gel activity assay. Except for higher activities of CAT, POX and APX, cotyledonary activities of CW-POX, mannanase and polygacturonase and to some extent β- 1, 4-D glucanase remained unaffected by HCN. Thus short term ROS accumulation in HCN-treated EA is due to declined SOD and POX activities. In long term the enhanced activities of both NADPH oxidase: CW-POX couple and cell wall-modifying enzymes in EA bring about wall loosening in preparation for radicle emergence. Evidences for the simultaneous operation of both mechanisms are provided in walnut EAs during dormancy release.
HCN 诱导的种子休眠解除需要改变活性氧（ROS）代谢和胚根细胞壁的松弛。关于 ROS 代谢与 HCN 诱导的种子休眠解除过程中细胞壁水解酶之间的相互作用知之甚少。因此，将休眠的核桃（Juglans regia L.）核仁暴露于 HCN（4 小时），并在 10 天的孵化期（即胚根出现之前）研究氧化还原代谢和细胞壁修饰酶。HCN 增加了 ROS，特别是在胚胎轴（EAs）中，但降低了产生 ROS 的 NADPH 氧化酶和 ROS 清除超氧化物歧化酶（SOD）和过氧化物酶（POX），对过氧化氢酶（CAT）、抗坏血酸过氧化物酶（APX）和细胞壁修饰酶的活性没有影响，在短期（最长 2 天）内没有影响。在长期内，从大约 4 天开始，HCN 暴露的 EA 显示出更多的超氧阴离子，并增强了 POX、APX、NADPH 氧化酶、细胞壁过氧化物酶（CW-POX）、β-1,4-D 葡聚糖酶、甘露聚糖酶、多聚半乳糖醛酸酶和木聚糖酶的活性。同时，通过凝胶活性测定发现，HCN 增加了 POX 和甘露聚糖酶同工型的更大表达。除了 CAT、POX 和 APX 的活性更高外，子叶 CW-POX、甘露聚糖酶和多聚半乳糖醛酸酶的活性以及在某种程度上β-1,4-D 葡聚糖酶不受 HCN 的影响。因此，HCN 处理的 EA 中短期 ROS 积累是由于 SOD 和 POX 活性下降所致。在长期内，EA 中 NADPH 氧化酶：CW-POX 偶联物和细胞壁修饰酶的活性增强导致细胞壁松弛，为胚根的出现做准备。在核桃 EA 中休眠释放过程中提供了这两种机制同时运作的证据。
