Abstract
MicroRNAs (miRNAs) have important roles in regulating stress-response genes in plants. However, identification of miRNAs and the corresponding target genes that are induced in response to cadmium (Cd) stress in Brassica napus remains limited. In the current study, we sequenced three small-RNA libraries from B. napus after 0 days, 1 days, and 3 days of Cd treatment. In total, 44 known miRNAs (belonging to 27 families) and 103 novel miRNAs were identified. A comprehensive analysis of miRNA expression profiles found 39 differentially expressed miRNAs between control and Cd-treated plants; 13 differentially expressed miRNAs were confirmed by qRT-PCR. Characterization of the corresponding target genes indicated functions in processes including transcription factor regulation, biotic stress response, ion homeostasis, and secondary metabolism. Furthermore, we propose a hypothetical model of the Cd-response mechanism in B. napus. Combined with qRT-PCR confirmation, our data suggested that miRNAs were involved in the regulations of TFs, biotic stress defense, ion homeostasis and secondary metabolism synthesis to respond Cd stress in B. napus.
Highlights
Increasing heavy metal pollution in aquatic and terrestrial environments, caused in part from the burning of fossil fuels and mining, has drawn worldwide attention [1]
In tobacco (Nicotiana spp.), over-expression of OsACA6 resulted in improved Cd2+ stress tolerance by maintaining cellular ion homeostasis and regulating the reactive oxygen species (ROS)-scavenging pathway [15]
Heavy metal stress signals induced through various pathways have been identified; these include mitogen-activated protein kinases (MAPKs) [16], hormones [17], Ca-calmodulin system [18], ROS signaling [19], and corresponding transcription factors (TFs) [20,21]
Summary
Increasing heavy metal pollution in aquatic and terrestrial environments, caused in part from the burning of fossil fuels and mining, has drawn worldwide attention [1]. Even though many miRNAs in B. napus have been revealed using high-throughput sequencing technology, heavy metal-regulated miRNAs (especially those related to Cd2+ stress) and corresponding target genes have not been entirely identified. An integrated schematic diagram was created based on differentially expressed miRNAs and corresponding target genes to better understand the regulation mechanisms related to Cd stress tolerance. These results extend our knowledge of miRNA-guided regulation of heavy metal stress responses in B. napus
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