Transcriptional regulation and expression network responding to cadmium stress in a Cd-tolerant perennial grass Poa Pratensis

Kentucky bluegrass has good capability to absorb and accumulate cadmium (Cd) through developed root system, thus having potential phytoremediation function in Cd contaminated soils. Understanding the molecular mechanisms of Cd tolerance and accumulation in this species will be crucial to generating novel Cd-tolerance cultivars through genetic improvement, while it has not well documented yet. In the present study, comparative transcriptome analysis was performed for the seedlings of high Cd-tolerant genotype (M) and low Cd-tolerant genotype (R) under Cd stress. A total of 7022 up-regulated and 1033 down-regulated transcripts were identified in M genotype, whereas, only 850 up-regulated and 846 down-regulated transcripts were detected in R. Further transcriptional regulation analysis in M genotype showed that Dof, MADS25, BBR-BPC, B3, bZIP23 and MYB30 might be the hub transcription factors in response to Cd stress due to the orchestrated multiple functional genes associated with carbohydrate, lipid and secondary metabolism, as well as signal transduction. Differential expressed genes involved in auxin, ethylene, brassinosteroid and ABA signalling formed signal transduction cascades, which interacted with hub transcription factors, thereby finally orchestrated the expression of multiple genes associated with cell wall and membrane stability, cell elongation and Cd tolerance, including IAAs, ARFs, SnRK2, PP2C, PIFs, BES1/BZR1, CCR, CAD, FATB, fabF and HACD. Additionally, post-transcriptional modification of CIPKs, MAPKs, WAXs, UBCs, and E3 ubiquitin ligases were identified and also involved in plant signalling pathways and abiotic resistance. The study could contribute to our understanding the transcriptional regulation and complex internal network associated with Cd tolerance in Kentucky bluegrass.