Abstract Fresh walnut seeds are vulnerable to germination during room-temperature storage, which can be delayed or inhibited by gamma radiation. However, the inhibitory mechanism involves the expression of multiple genes and remains unclear. ‘Liaohe 2’ fresh walnut seeds were exposed to a wide-spectrum dose of 60Co gamma rays and then stored in sand under a suitable humidity at 25 ± 1 °C. Six transcriptome libraries of walnut embryos irradiated at 0 and 50 Gy were investigated at 0, 6 and 12 d of storage using RNA-seq. The results showed that a total of 177 differentially expressed genes (DEGs) was detected between the GR0d vs CK0d seeds. With gamma radiation, 471 genes were upregulated and 2835 genes could not be upregulated during the germination of untreated walnuts. Additionally, 1212 genes could not be downregulated, and 166 genes were downregulated. Glutathione and non-homologous end-joining were upregulated immediately after gamma radiation. In total, 23 upregulated genes related to reactive oxygen species (ROS) scavenging and signal transduction pathways were identified during early seed germination, and 79 genes related to ribosomal proteins could not be upregulated at 6 d after gamma radiation. The levels of both abscisic acid (ABA) and gibberellin (GA3) increased rapidly at 0 d, and the w(GA3)/w(ABA) ratio decreased significantly at 12 d after gamma radiation. In conclusion, a possible mechanism by which gamma radiation inhibits the germination of fresh walnuts was proposed as follows: gamma radiation first induced a series of stress responses, including the ROS scavenging system and TFs, and prevented the upregulated expression of ribosomal protein genes from 0 to 6 d, resulting in the inhibition of cell division, which is a likely key starting point for germination inhibition. Finally, a hormonal imbalance occurred, and the suppression of the upregulation of stored lipid breakdown genes from 6 to 12 d in treated nuts is proposed as the critical reason for the inhibition of fresh walnut germination by gamma radiation.

中文翻译：

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储存期间胚胎转录组学分析发现伽马辐射对新鲜核桃 (Juglans regia) 早期萌发抑制的机制

摘要 新鲜核桃种子在常温贮藏过程中容易发芽，受伽马射线的影响可能会延迟或抑制发芽。然而，其抑制机制涉及多个基因的表达，目前尚不清楚。'辽河 2 号'新鲜核桃种子暴露于广谱剂量的 60Co 伽马射线，然后在适当湿度下在 25±1°C 的沙子中储存。使用 RNA-seq 在储存的 0、6 和 12 天研究了六个以 0 和 50 Gy 辐照的核桃胚胎转录组文库。结果表明，在 GR0d 与 CK0d 种子之间共检测到 177 个差异表达基因（DEGs）。在未经处理的核桃发芽过程中，伽马辐射有 471 个基因上调，2835 个基因无法上调。此外，1212个基因不能被下调，166 个基因被下调。谷胱甘肽和非同源末端连接在伽马辐射后立即上调。在早期种子萌发过程中，总共鉴定出 23 个与活性氧 (ROS) 清除和信号转导途径相关的上调基因，79 个与核糖体蛋白相关的基因在伽马辐射后 6 d 无法上调。脱落酸（ABA）和赤霉素（GA3）的水平在0 d时迅速增加，并且在γ辐射后12 d时w（GA3）/w（ABA）比值显着下降。综上所述，伽马辐射抑制新鲜核桃萌发的可能机制如下：伽马辐射首先诱导了一系列应激反应，包括ROS清除系统和TFs，并阻止核糖体蛋白基因从 0 到 6 天的上调表达，从而抑制细胞分裂，这可能是抑制萌发的关键起点。最后，发生了荷尔蒙失衡，并且在 6 至 12 d 处理过的坚果中抑制储存的脂质分解基因的上调被认为是伽马辐射抑制新鲜核桃发芽的关键原因。