Identification of heavy metal-responsive genes in radish (Raphanus sativus L.) through RNA-Seq meta-analysis

Abstract

Abstract Heavy metals (HMs) are essential to plant life in suitable amounts, but cellular damage might be caused by excess amounts of HMs. In recent years, most reports on unique metal stresses, such as chromium (Cr), lead (Pb) and cadmium (Cd), have utilized radish, especially Liwang Liu s laboratory. However, major activated genes related to HM stress shared in Cr, Pb and Cd stress and their related specific pathways are urgently required in radish. Herein, according to FPKM for four transcriptomes collected from Liu s laboratory, 46 DEGs related to HM stress genes shared among heavy metal (Cr, Cd and Pb) treatments were identified, together with 66 HM-induced genes, comprising those for functional proteins and transcription factors (TFs). Of these genes, 12 DEGs related to the HM stress response were validated using quantitative real-time PCR. The results showed that WRKY33 was significantly changed in response to heavy metal stress (Cr, Cd and Pb) treatment after 24 h in both the sensitive material ‘Hongxin 1’ and the resistant material ‘XCB’. Similar trends were also identified for transcripts of PIN1 protein, MRP protein and ABC transporter. Conversely, the transcripts of LCC4, bHLH143 and GST were found to be significantly changed in the sensitive material ‘Hongxin 1’ compared with the resistant material ‘XCB’ treated at different time points (0 h, 12 h, 24 h, 36 h, 48 h and 72 h). However, ARF1 and ERF-rap2.7 transcripts were found to be significantly decreased after 24 h of treatment in ‘Xichangbai 1’ compared with ‘Hongxin 1’ after heavy metal stress. In addition, most of the DEGs were found to be significantly enriched in the GO terms cellular response to extracellular stimulus, response to extracellular stimulus, auxin mediated signaling pathway, cellular response to chemical stimulus and response to oxidative stress through GO enrichment analysis. These results will expand our understanding of plant responsiveness to HM stress in radish under Cr, Pb and Cd stress and facilitate further genetic manipulation of HM stress genes on uptake and accumulation in radish.