Genome Wide Transcriptome Analysis of tef (Eragrostis tef) Under Long-Term Low Calcium Stress

Calcium (Ca2+) is one of the essential mineral nutrients for plant growth and development. However, the effects of long-term Ca2+ deficiency in orphan crops such as tef (Zucc.) Trotter] which accumulate high levels of Fe in the grains remained unknown. Tef is a staple crop for nearly 70 million people in East Africa, particularly Ethiopia and Eritrea. It is rich in mineral nutrients (Ca+2, Fe, Zn and Mn), vitamins and essential amino acids. In this study, tef plants were grown in hydroponic solution containing optimum (1 mM) or low (0.01 mM) Ca2+ and plant growth parameters and whole genome transcriptome were analyzed. Ca+2-deficient plants exhibited symptoms including leaf necrosis, leaf curling, and growth stunting. Ca2+ deficiency significantly decreased root and shoot Ca+2, potassium (K) and copper content in both root and shoots while it significantly increased root iron (Fe2+) content, suggesting the role of Ca2+ in the uptake and/or translocation of these minerals. Transcriptomic analysis using RNA-seq revealed that members of Ca2+ channels including the cyclic nucleotide-gated channels (CNGC) and glutamate receptor-like channels (GLRs), Ca2+-transporters, Ca2+-binding proteins (CBP) and Ca2+-dependent protein kinases (CDPK) were differentially regulated by Ca+2 treatment. Moreover, several Fe/metal transporters including members of vacuolar Fe transporters (VIT), yellow stripe-like (YSL), natural resistance-associated macrophage protein (NRAMP) and oligo-peptide transporters (OPT) were differentially regulated between shoot and root in response to Ca2+ treatment. Taken together, our findings suggest that Ca2+ deficiency affects plant growth and mineral accumulation by regulating the transcriptomes of several transporters and signaling genes. N = 4 SAMPLES PER TREATMENT GROUP