The Preliminary Function Analysis Of TaRopl, As Small GTP Binding Protein In Wheat

Small GTP-binding proteins play important roles in eukaryotic organisms as molecular switches.There are two forms of small GTP-binding proteins, inactive GDP-bound and active GTP-bound form,by which regulating a wide variety of signaling and metabolic progresses through downstream effectors.According to the structures and functions, small GTP-binding proteins can be classified into fivefamilies: the Ras, Ran, Arf, Rab and Rho. Rop (Rho of plants) proteins, derived from plants, consist of aplant-specific small GTP-binding protein family, having high similarities to the Rho family membersand be called as “Rac family” in plants. At present, Rop proteins have been found in varieties of plantspecies such as rice, Arabdopsis thaliana, barley, maize, tobacco, Medicago sativa, and their structuresand functions have been studies deeply. It have been found that Rop proteins involved in biologicalregulation processes, such as cell polar growth, cytokinesis, hormone signaling, interactions betweenplant hosts and pathogens. According to the planting area and production, wheat is the third cereal cropin China, but it is threatened by fungal diseases such as stripe rust and abiotic stresses. In this study wecloned a Rop gene from bread wheat and analyzed its functions in the disease resistance and abiotictolerance. It will provide an alternative gene for developing stress resistance wheat varieties.In this study, we conducted the primary biological functions of a gene TaRop1encoding Rop smallGTP-binding protein derived from a near-isogenic line of stripe rust resistance gene Yr5. We analyzedtissue-specific expression patterns of TaRop1in wheat and those under biotic and abiotic stressconditions by semi RT-PCR. In additions, we analyzed the functions of TaRop1in disease resistance anddrought tolerance ability using overespression transgenic tobacco (Nicotiana benthamiana) lines.The research results mainly include two parts. Firstly, TaRop1expressed in wheat root, stem andleaf in both seedling and adult plant stages. It was also found in stigma and internode, but little isdetected in anther. TaRop1expression was induced by incompatible race CYR17of Puccinia striiformis,MeJA, drought, high temperature and wounding, while inhibited by ET and ABA treatments. SAtreatment reduced TaRop1expression level slightly. Secondly, compared with the wild type, the lesiondevelopment was inhibited and the number of bacterial colonies reduced in the overexpressiontransgenic lines after inoculated with virulent strain NNYH5of Pseudomonas syringae pv. tabaci.However, when inoculated with the an avirulent strain DC3000of Pseudomonas syringae pv. Tomato,to which Nicotiana benthamiana is non-host resistant, accumulation level of ROS in the overexpressiontransgenic tobacco lines is higher than the wild type and non-host hypersensitive response (HR)appeared earlier. Besides, compared with control plants, malonic dialdehyde (MDA) content increasedand relative water content (RWC) decreases slightly respectively in transgenic tobacco linesoverexpressing TaRop1under drought stress condition, which showed higher drought tolerance.In summary, wheat TaRop1encoding a small GTP-binding protein was involved in interactionsbetween plant host and its pathogens, abiotic stress responses and exogenous plant hormone treatments.Overespressing TaRop1could enhance transgenic tobacco lines resistance to bacterial PstNNYH5, promote HR to PstDC3000and increase ROS accumulation. These results suggest that TaRop1playpositive roles in regulations of plant responses to biotic and abiotic stresses.