Abstract
BackgroundCadmium translocation from roots to shoots is a complex biological process that is controlled by gene regulatory networks. Pak choi exhibits wide cultivar variations in Cd accumulation. However, the molecular mechanism involved in cadmium translocation and accumulation is still unclear. To isolate differentially expressed genes (DEGs) involved in transporter-mediated regulatory mechanisms of Cd translocation in two contrasting pak choi cultivars, Baiyewuyueman (B, high Cd accumulator) and Kuishan’aijiaoheiye (K, low Cd accumulator), eight cDNA libraries from the roots of two cultivars were constructed and sequenced by RNA-sequencing.ResultsA total of 244,190 unigenes were obtained. Of them, 6827 DEGs, including BCd10 vs. BCd0 (690), KCd10 vs. KCd0 (2733), KCd0 vs. BCd0 (2919), and KCd10 vs. BCd10 (3455), were identified. Regulatory roles of these DEGs were annotated and clarified through GO and KEEG enrichment analysis. Interestingly, 135 DEGs encoding ion transport (i.e. ZIPs, P1B-type ATPase and MTPs) related proteins were identified. The expression patterns of ten critical genes were validated using RT-qPCR analysis. Furthermore, a putative model of cadmium translocation regulatory network in pak choi was proposed.ConclusionsHigh Cd cultivar (Baiyewuyueman) showed higher expression levels in plasma membrane-localized transport genes (i.e., ZIP2, ZIP3, IRT1, HMA2 and HMA4) and tonoplast-localized transport genes (i.e., CAX4, HMA3, MRP7, MTP3 and COPT5) than low Cd cultivar (Kuishan’aijiaoheiye). These genes, therefore, might be involved in root-to-shoot Cd translocation in pak choi.
Highlights
Cadmium translocation from roots to shoots is a complex biological process that is controlled by gene regulatory networks
The member of Natural resistance-associated macrophage protein (Nramp) family in rice, OsNramp1 [12] and OsNramp5 [13,14,15] were reported to be Cd transporter involved in the root uptake of Cd from the medium. These findings suggested that a number of metal-regulated transporter proteins could participate in cellular Cd uptake and translocation within plants
After filtering the reads with low quality and adapters, the percentages of clean reads in all eight transcriptomes were all above 95.99%, and the proportion of Q20 bases for the clean reads was above 95.93% for each library (Table 1)
Summary
Cadmium translocation from roots to shoots is a complex biological process that is controlled by gene regulatory networks. Several processes are involved in the distribution and translocation of Cd in plant roots [6,7,8], including (i) transporter-mediated Cd translocation via symplasmic or apoplastic pathway; (ii) deposition of Cd in the cell wall; and (iii) sequestration of Cd-chelates in the vacuole. Most of these processes are mediated by transportrelated genes. OsHMA3 plays a role in the sequestration of Cd into
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