Institute of Dendrology, Polish Academy of Sciences, Parkowa 5, 62-035 Kórnik, Poland.
Department of Forestry, Faculty of Agriculture and Natural Resources, Lorestan University, Khorramabad, Iran.
Plant Cell Physiol. 2020 Jun 1;61(6):1158-1167. doi: 10.1093/pcp/pcaa044.
Desiccation tolerance is a developmental program enabling seed survival in a dry state and is common in seeds categorized as orthodox. We focused on NAD and its phosphorylated form (NADP) because their continual switching between reduced (NAD(P)H) and oxidized (NAD(P)+) forms is involved in the modulation of redox signaling and the determination of the reducing power and further antioxidant responses. Norway maple and sycamore seeds representing the orthodox and recalcitrant categories, respectively, were used as models in a comparison of responses to water loss. The process of desiccation up to 10% water content (WC) was monitored in Norway maple seeds, while dehydration up to 30% WC was monitored in desiccation-sensitive sycamore seeds. Norway maple and sycamore seeds, particularly their embryonic axes, exhibited a distinct redox status during dehydration and desiccation. High NADPH levels, NAD+ accumulation, low and stable NAD(P)H/NAD(P)+ ratios expressed as reducing power and high NADPH-dependent enzyme activity were reported in Norway maple seeds and were considered attributes of orthodox-type seeds. The contrasting results of sycamore seeds contributed to their low antioxidant capacity and high sensitivity to desiccation. NADPH deficiency, low NADPH-dependent enzyme activity and lack of NAD+ accumulation were primary features of sycamore seeds, with implications for their NAD(P)H/NAD(P)+ ratios and reducing power and with effects on many seed traits. Thus, we propose that the distinct levels of pyridine nucleotides and their redox status contribute to orthodox and recalcitrant phenotype differentiation in seeds by affecting cellular redox signaling, metabolism and the antioxidant system.
脱水耐性是一种使种子在干燥状态下存活的发育程序，在被归类为正统的种子中很常见。我们专注于 NAD 和其磷酸化形式（NADP），因为它们在还原（NAD(P)H）和氧化（NAD(P)+）形式之间的持续转换涉及氧化还原信号的调节和还原力的确定以及进一步的抗氧化反应。挪威枫和梧桐种子分别代表正统和顽固类别，被用作比较水分损失反应的模型。在挪威枫种子中监测了脱水至 10%含水量（WC）的过程，而在脱水敏感的梧桐种子中监测了脱水至 30%WC 的过程。挪威枫和梧桐种子，特别是它们的胚胎轴，在脱水和干燥过程中表现出明显的氧化还原状态。在挪威枫种子中报告了高水平的 NADPH、NAD+积累、低且稳定的 NAD(P)H/NAD(P)+比（表示还原力）和高水平的 NADPH 依赖性酶活性，被认为是正统型种子的特征。梧桐种子的对比结果导致其抗氧化能力低和对干燥敏感。NADPH 缺乏、低 NADPH 依赖性酶活性和缺乏 NAD+积累是梧桐种子的主要特征，对其 NAD(P)H/NAD(P)+比和还原力有影响，并对许多种子特性产生影响。因此，我们提出，吡啶核苷酸的不同水平及其氧化还原状态通过影响细胞氧化还原信号、代谢和抗氧化系统，有助于正统和顽固表型的分化。
