Preliminary Study Of Banana Small GTPases Gene MaROP1 In Transgenic Arabidopsis

The small GTPases of ROP (Rho-related GTPases from plants) are important regulators of signaling pathways and developmental processes in plants. MaROP1, a member of ROP, was isolated from the suppression subtractive hybridization library of the banana fruit. MaROP1 had a complete open reading frame encoding 196 amino acids, with conserved domains of ROP, Blastx showed that MaROP1 had a high degree of sequence similarity with ROP from other plants. The previous study in our lab demonstrated that MaROP1 had a low copy number in the banana genome and was differentially expressed in root, rhizome, leaf, flower and fruit of banana with much higher expressed in rhizome than any other organ.To understand the function of MaROP1 in respone to stress tolerance and plant hormones, plant expression vector pCAMBIA1302-MaROP1 was constructed and transformed into the wild type Arabidopsis thaliana (columbia ecotype) using a Agrobaterium tumefaciens EHA105 mediated transformation by the floral dipping method. After generations of seeds (T1-T3) selected on MS medium containing 35 ug/mL hygromycin B, we obtained the homozygous transgenic lines of Arabidopsis thaliana, southern boltting indicated MaROP1 gene had been integrated into the genome of the homozygous transgenic lines, RT-PCR confirmed MaROP1 gene was stably expressed in the homozygous transgenic lines.MaROP1 transgenic Arabidopsis thaliana lines showed inhanced resistance to salt stress compared with the wild type.The seed germination rate of the transgenic lines was higher than the wild type under different concentrations of NaCl. With 200mM NaCl treatment, the germination rate of the wild type was 23.42%, the germination rate of the transgenic lines was between 46.21% and 79.76%.The inhibition of the transgenic lines root length by NaCl of was lower compared with the wild type. With 150mM NaCl treatment, the average root length of wild-type was 0.29 cm, the transgenic lines was between 0.57 and 0.79 cm. Under salt stress, the survival rate of transgenic line seedling was higher than the wild type seedling, treated with 300mM NaCl for 14 days, the survival rate of the wild type was almost zero, while the transgenic lines was above 30%.MaROP1 Arabidopsis thaliana transgenic lines increased resistance to drought stress compared with the wild type.The seed germination rate of the transgenic lines was higher than the wild type under different concentrations of mannitol. With 400mM mannitol treatment, the germination rate of the wild type was 23.12%, the germination rate of the transgenic lines was between 73.83% and 85.00%.The inhibition of the transgenic lines root length by mannitol of was lower compared with the wild type. With 400mM mannitol treatment, the root length of the wild type was almost zero, the transgenic lines was between 1.00 and 1.42 cm. The water loss rate of detached leaves from the transgenic lines was decreased in comparison with the wild type. The water loss rate of the wild type was 38.07% treated for 240min while the transgenic lines was between 22.04% and 29.43%. Under drought stress, the survival rate of the transgenic lines (35%-65%) was higher than the wild type (16%).MaROP1 Arabidopsis thaliana transgenic lines reduces ABA sensitivity compared with the wild type.Seed germination experiment showed that MaROP1 transgenic lines decreased sensitivity to endogenous ABA compared with the wild type.Under ABA treatment, the seed germination rate of transgenic lines were higher than the wild type. With 5 uM ABA treatment, the germination rate of the wild type was 38.77%, while the transgenic lines was between 54.62% and 70%.The root of transgenic lines were longer and the growth of cotyledon were better than the wild type.