Transcriptome analysis of salt stress responsiveness in the seedlings of wild and cultivated Ricinus communis L

Soil salinity is one of the major environmental factors, influencing agricultural productivity of crops. As a non edible and ideal oilseed crop, castor (Ricinus communis L.) has great industrial value in biofuel, but molecular mechanisms of salt stress regulation are still unknown. In this study, the differentially expressed genes (DEGs) for differential salt tolerance in two castor cultivar (wild castor : Y, cultivated castor 'Tongbi 5': Z) were identified. 12 libraries were sampled for Illumina high-throughput sequencing to consider 132,426 nonredundant unigenes and 31,221 gene loci. Multiple phytohormones and transcription factors (TFs) were correlated with salt-tolerance and differently enriched in these two genotypes. The type 2C protein phosphatases (PP2C) homologs were all upregulated under salt stress. Importantly, IAA (1), DELLA (1) and Jasmonate zim domain (JAZ) (1) were also identified and found to be differentially expressed. Based on the co-expressed module by regulatory networks and heatmap analysis, ERF/AP2, WRKY and bHLH families were prominently participate in high salt stress response of wild and cultivated castor. Finally, these results highlight that the hub DEGs and families were more accumulated in cultivated castor than those in wild castor, providing novel insights into the salinity adaptive mechanisms and genetic improvement in castor.

Automated summary

This study identified differentially expressed genes associated with salt tolerance in two castor cultivars through high-throughput sequencing, revealing the involvement of various phytohormones and transcription factors in salt tolerance mechanisms. The upregulation of type 2C protein phosphatases under salt stress and the differential expression of IAA, DELLA, and JAZ were also observed. Regulatory networks analysis indicated the participation of ERF/AP2, WRKY, and bHLH gene families in high salt stress response in both wild and cultivated castor, with more accumulation of hub DEGs and families in cultivated castor compared to wild castor.