Abstract One of the main pathways for cadmium (Cd) transfer from the environment to the humans is through the consumption of leafy vegetables, and Brassica leafy crops tend to be Cd hyper-accumulators. To investigate Brassica response strategies to Cd, two cultivars with different Cd tolerance were used to perform transcriptomic studies under Cd treatments. Genes related to vacuolar sequestration (such as ABCCs and YSL family genes) and detoxification (such as GST, SAT and APS) were up-regulated in both cultivars but exhibited different temporal expression profiles in leaves of the two cultivars, which may underlie their different Cd tolerance. Analyses of microRNAs (miRNAs) and their target genes by small RNA and degradome sequencing not only revealed Cd-induced changes in miRNAs but also implicated the existence of a regulatory cascade involving two miRNAs, bra-miR156 and bra-miR397, and their corresponding targets, SPLs and LACs, in Cd stress responses. This cascade down-regulates the expression of several LACs particularly in roots under Cd stress, and it is proposed to be a mechanism to maintain root growth under Cd stress through regulating cell wall lignification. In addition, Cd induced a drastic reduction of a 22-nt small RNA, the footprint of a pentatricopeptide repeat (PPR) protein on the chloroplast ndhB transcript and the concomitant down-regulation of the ndhB transcript. A global reduction in the expression of PPR genes was found, revealing previously unknown effects of Cd on organellar gene expression. The present findings help uncover the impact of Cd stress on the transcriptome of B. parachinensis and reveal the strategies used by B. parachinensis in dealing with Cd stress. It also provides candidate genes and miRNAs for further investigation.

中文翻译：

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全基因组 mRNA 和小 RNA 转录组谱揭示了白菜中镉诱导的栽培品种和组织特异性变化

摘要 镉 (Cd) 从环境转移到人类的主要途径之一是通过食用叶类蔬菜，而芸苔属叶类作物往往是 Cd 超蓄积者。为了研究芸苔属植物对 Cd 的响应策略，使用具有不同 Cd 耐受性的两个栽培品种在 Cd 处理下进行转录组学研究。与液泡隔离（如 ABCCs 和 YSL 家族基因）和解毒（如 GST、SAT 和 APS）相关的基因在两个品种中均上调，但在两个品种的叶片中表现出不同的时间表达谱，这可能是它们不同的原因。镉耐受性。通过小 RNA 和降解组测序对 microRNA (miRNA) 及其靶基因的分析不仅揭示了 Cd 诱导的 miRNA 变化，而且还暗示存在涉及两个 miRNA、bra-miR156 和 bra-miR397 及其相应靶标的调控级联反应、SPL 和 LAC，在 Cd 应激反应中。这种级联下调了几种 LACs 的表达，尤其是在镉胁迫下的根中，它被认为是通过调节细胞壁木质化来维持根在镉胁迫下生长的机制。此外，Cd 诱导 22 nt 小 RNA、叶绿体 ndhB 转录物上五角肽重复 (PPR) 蛋白的足迹以及随之而来的 ndhB 转录物下调。发现 PPR 基因表达的整体减少，揭示了以前未知的 Cd 对细胞器基因表达的影响。目前的研究结果有助于揭示 Cd 胁迫对 B. parachinensis 转录组的影响，并揭示 B. parachinensis 在处理 Cd 胁迫时使用的策略。它还提供了候选基因和 miRNA 以供进一步研究。