Functional Genomics of Seedling Cold Adaptation in Sorghum bicolor

Crops originated in the tropical and sub-tropical regions are sensitive to cold. However, few of these crops have evolved mechanisms to sustain low temperatures. To understand the mechanistic basis of cold adaptation in crops of tropical origin, we took advantage of sorghum, a C4 tropical grass originated in Africa. Owing to its origin, sorghum adapted to marginal soils, drought and high temperatures. In contrast, it is extremely susceptible to cooler temperatures, below 10 ⁰C (Peacock, 1982). In sorghum, cold tolerance was identified in Kaoliang Chinese landraces (Singh 1985). Our research utilizes functional genomic approaches: transcriptomics and lipidomics, to understand the mechanistic basis of seedling cold adaptation.

To evaluate the transcriptome, two-week-old seedlings of cold tolerant Chinese landrace NuiSheng Zui (NSZ) and cold susceptible BTx623 inbred were subjected to 36 h cold (10/8 ⁰C day/night). While NSZ and BTx623 seedlings maintained at 28/25 ⁰C were used as the controls. Transcriptome analysis was done using iPlant DNA Subway pipeline and GSNAP/HTSeq/DESeq2. Under cold stress, 874 genes were differentially regulated in NSZ in comparison with BTx623. Gene Ontology and MapMan analysis suggested that cold tolerance is possibly conferred by lipid localization and remodeling. Therefore, lipidome of four cold tolerant Chinese accessions and two cold susceptible US accessions under optimal and cold stress was conducted. Combined lipidome and transcriptome results suggest that lipid remodeling may be responsible for cold tolerance in sorghum, as observed in Arabidopsis. The functional genomics data obtained from our research can aid in developing seedling cold tolerance in tropical crops.