Rice genetic engineering using transformation of Deeper Rooting1 and Phosphorus-Starvation Tolerance1 genes

Root structure modification is associated with the efficient water uptake and the nutrient utilization. It also provides structural support for the anchoring in soil. Genetic engineering for the improvement of plant root structure may help to maintain higher yields under drought conditions. The aim of this study was to modify the root structure of rice in order to improve drought tolerance and the efficiency of nutrient uptake. For this purpose, simultaneous transformation of Deeper Rooting1 or OsDRO1 gene, which is involved in the regulation of growth angle of the root in order to adapt to drought conditions, and Phosphorus-Starvation Tolerance1 or OsPSTOL1 gene, which is effective in increasing phosphorus uptake and improving root structure, were considered for rice root structure modification. 

The OsDRO1 and OsPSTOL1 genes derived from the wild rice cultivars were cloned together in a single construct under the control of the root specific and the ubiquitin promoters, respectively. The resulting construct, pUhrDroPstol is transformed into the Agrobacterium tumefactions strain EHA105 and used for the gene transformation into Hashemi cultivar. Putative transgenic plants, survived on 50 mg/L Hygromycin during tissue culture steps, are transplanted into the Yoshida solution and then into the pots until they set seeds. Construct specific and gene specific PCR analysis are used to confirm the transgenic plants. 

In this study, 12 putative transgenic rice events were obtained, of which 10 showed the presence of both OsDRO1 and OsPSTOL1 genes in the PCR analysis. Transgenic plants show stronger root structure compared to the non-transgenic ones. Molecular analysis in the T1 and T2 generations determined the homozygous events. 

In this study, two candidate genes affecting root structure, nutrient uptake and drought tolerance were transferred to the Hashemi rice using genetic engineering. So far, simultaneous transfer of these two candidate genes have not been reported. Transgenic plants present better root system compared to the control plants. The mentioned construct can be used for the transformation of other crops to improve their root structure, nutrient uptake and their drought tolerance. It is hoped that the production of the transgenic rice with modified root structure and efficient phosphorus uptake increases its drought tolerance and reduce water consumption in rice cultivation.