Resistance Identification Of Transgenic Rice Plants Expressing Antibody Fusions After Inoculation With Rice Bakanae Pathogens

The fungus Fusarium verticillioides (Sacc.) Nirenbert, formerly known as F. moniliforme J. Sheld., is an important fungal pathogen of rice and the causal agent of the bakanae disease. Due to bakanae, 10%-20% of the rice yields have been lost in China and some times as high as 50%. F. verticillioides causes a decrease not only in quantity but also in quality of rice by producing toxins, such as fumonisins, moniliformin, fusarin C and fusaric acid, that affect human and animal health. However, no rice cultivar has high innate immunity to bakanae disease, therefore, often use fungicides for rice protection in modern agriculture. The repeated use of hazardous agrochemicals for the control of this disease has several drawbacks such as their lack of specicity, increased incidence of development of resistance upon prolonged appli-cation and the adverse impact on human health and the environment. Plant genetic engineering provides an opportunity to introduce novel genes into rice cultivars, particularly genes conferring disease resistance. The transgenic rice plant exhibite better control of F. verticillioides.In the previous work of our laboratory, an antibody fusion protein comprising a Fusarium-specific recombinant antibody and an AFP from Aspergillus giganteus (AG) and an AFP from Raphanus sativus (Rs) were introduced into rice genome. Constitutive expression in planta regulated by the maize Ubiquitin promoter would provide a continual supply of the antibody fusion proteins that were secreted into apoplast. The transgenic rice TO plants were screened.In this study, the genetic stability analysis of the antibody fusion gene and further screening of resistant lines in transgenic offspring were carried out. Firstly, PCR assay detect F. verticillioides strains using two pairs of specific primers for F. verticillioides and fumonisin-producing F. verticillioides strains. Eight strains of F. verticillioides from the laboratory were tested using both sets of primers. Using primer antibody fusion gene D2, the PCR detection and Southern blotting analysis of the T2 transgenic rice plant lines showed that antibody fusion gene had benn integrated into the rice genome in line 3, 4, 5, 8, 31, 34, 38, 46, 47 and 49. The RT-PCR detection of the T2 transgenic rice lines showed that the fusion protein genes had been well expressed. Inoculation with the F. verticillioides, transformants exhibited resistance to rice bakanae at various levels.As no rice cultivar has innate immunity to bakanae, our results demonstrated that the antibody fusion protein may be used as an effective tool for the protecion of crops against rice bakanae fungus F. verticillioides.