Abstract Worldwide contamination of agricultural soils with cadmium (Cd) not only leads to reduced plant yield, but accumulation within the edible plant parts also poses a serious threat to human health. In this study, the rice leaf growth zone was used to examine how the effects of Cd on leaf growth are mediated by its effect on cell division and expansion. Based on a kinematic analysis and flow cytometry, we show that both processes are inhibited upon root Cd exposure. The Cd-inhibited leaf growth was confirmed by the overall downregulation of cell cycle genes upon Cd exposure. In addition, Cd preferentially accumulates within the leaf meristem and the transition zone, whereas the concentration steeply drops in the elongation zone. As Cd induces an oxidative challenge, which is also related to plant growth, it was further investigated whether this could be involved in the mode of action of the Cd-inhibited leaf growth. Therefore, gene expression patterns of antioxidative enzymes such as superoxide dismutases (SOD), catalases (CAT) and ascorbate peroxidases (APX) were investigated in different leaf growth zones. Whereas no significant differences were seen for SOD expression across the different leaf zones under control conditions, large differences in abundance were visible for APX and CAT expression. Moreover, Cd stress significantly upregulated genes in these families in an isoform- and location-dependent fashion, indicating the possible involvement of the Cd-induced oxidative challenge in regulating leaf growth processes and highlighting the importance of specific leaf sampling for further investigations.

中文翻译：

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受控和镉暴露条件下水稻叶片生长区的空间分析

摘要 世界范围内农业土壤中镉 (Cd) 的污染不仅导致植物产量下降，而且可食用植物部分内的积累也对人类健康构成严重威胁。在这项研究中，水稻叶片生长区被用来研究 Cd 对叶片生长的影响是如何通过其对细胞分裂和扩张的影响来介导的。基于运动学分析和流式细胞术，我们表明这两个过程在根接触 Cd 时都受到抑制。镉抑制的叶片生长通过镉暴露后细胞周期基因的整体下调得到证实。此外，Cd 优先在叶片分生组织和过渡区积累，而在伸长区浓度急剧下降。由于 Cd 诱导氧化挑战，这也与植物生长有关，进一步研究了这是否可能与 Cd 抑制叶片生长的作用方式有关。因此，研究了抗氧化酶如超氧化物歧化酶 (SOD)、过氧化氢酶 (CAT) 和抗坏血酸过氧化物酶 (APX) 在不同叶片生长区的基因表达模式。虽然在对照条件下不同叶区的 SOD 表达没有显着差异，但 APX 和 CAT 表达的丰度差异很大。此外，镉胁迫以亚型和位置依赖性方式显着上调这些家族中的基因，表明镉诱导的氧化挑战可能参与调节叶片生长过程，并突出了特定叶片采样对进一步研究的重要性。