Identification and characterization of cold shock domain proteins (CSPs) for their response to cold stress in pigeonpea [Cajanus cajan (L.) Millsp.]

Chilling stress arrests plant metabolism, slowly perturbing homeostasis, which eventually leads to senescence. If imposed for a long time, it can cause plant death. Prokaryotes possess cold shock domain-containing proteins (CSPs) in their genomes that help them acclimate to chilling stress by acting as RNA chaperones, ensuring the maintenance of cellular functions. Considering this as an important class of genes in maintaining homeostasis during chilling stress, the present study was conducted to carry out a genome-wide survey of these genes in Cajanus cajan, which has not been studied to date. In-silico genome-wide characterization of the Cajanus genome identified 4 CSPs (CcCSP1, CcCSP2, CcCSP3 and CcCSP4) members. Domains prediction identified each containing at least one CSD (cold shock domain), Glycine-rich repeats and CCHC-type zinc fingers, suggesting their role as nucleic acid binding proteins and protein-protein interactions. All, except the CcCSP2 gene, were found to be intronless. Additionally, CcCSP2 was found to be divergent from the rest of the three genes and phylogenetically close to Medicago MtCSP3. Spatiotemporal expression in genotypes contrasting for cold stress response showed the highest expression of the CcCSP2 gene (almost 6-fold) in flowering bud tissue of tolerant genotypes, suggesting it may be involved in the cold adaptation mechanism. The study establishes that less-explored cold acclimation proteins, such as CSPs, are transcriptionally regulated genes in Cajanus when it experiences chilling stress during extreme weather conditions. This suggests that this subtropical crop may have the potential to cold-acclimate. Further studies are needed to establish the details so that crop damage is mitigated in these times of climate change.