Sorghum bicolor L. is an important crop in many tropical regions, yet it has received little attention in applying modern biotechnologies for improvement due to transformation difficulties. Drought is among the most important factors limiting sorghum productivity. The Nicotina Protein Kinase 1 (NPK1) gene confers tolerance to adverse environmental conditions. The present work was conducted to determine the amenability of sorghum genotypes to Agrobacterium-mediated transformation with the NPK1 gene and to characterize the role of that gene in S. bicolor. The NPK1 gene along with the bar gene was successfully introduced into two sorghum genotypes: Dorado and SPGM94021. The transformation frequencies were 1.49 and 1.79% for Dorado and SPGM94021, respectively. Stable integration of the transgenes in T0 and T1 plants was confirmed through polymerase chain reaction (PCR) and Southern blotting. The NPK1 gene expression was measured through real-time-PCR. T1 plants tested in vitro for tolerance to mannitol osmotic stress maintaining a higher growth rate and showed increased tolerance to stress conditions compared to the non-transgenic plants. The transgenic sorghum had a significantly higher kernel weight under drought stress conditions than the control plants. Accordingly, the NPK1 gene might induce a mechanism that protects sorghum plants against possible water-deficiency stress conditions.
Key words: Abiotic stress related genes, regulatory genes, signal transduction, transgenic sorghum, plant transformation, quantitative real time-polymerase chain reaction (qRT-PCR), drought stress tolerance.
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