Functional Identification Of The Gene Involved In Positively Regulating Systemic Acquired Resistance Of Rice

The NPRl gene was isolated by positional cloning from Arabidopsis thaliana by Cao et al. in 1997. It is a key regulator for systemic acquired resistance of Arabidopsis thaliana. Upon induction, NPRJ expression is elevated and the NPRl protein is activated, in turn inducing expression of a battery of downstream pathogenesis-related genes. Overexpression of NPRl in Arabidopsis thaliana leads to enhanced disease resistance with no obvious detrimental effect on the plant.In this work, we cloned an Arabidopsis NPRl homologous gene from rice cultivar Gui99 in the vector of pCAMBIA1301-35SN in antisense orientation to get a rice expression vector. The antisense gene was introduced to Gui99 by Agrobacterium twnefaciens mediated transformation. Upon hygromycin selection, some hygromycin-resistant calli were obtained, and seven hygromycin-resistace plantlets regenerated. PCR and sequencing analysis of PCR products indicated that six out of the seven hygromycin-resistant plants are transgenic. The transgenic rice plants were inoculated with Xanthmonas oryzae pv. oryzae Chinese strain 13 751. The lesion lengths of the diseased leaves were recorded 14 days post inoculation. Analysis of variance showed that the lesion lengths of the six transgenic rice plants are significantly longer than those of nontransgenic rice plants, indicating that the expressed antisense gene in rice enabled the plants to be more susceptible to Xanthmonas oryzae pv. oryzae Chinese strain 13 751. Therefore, all these data confirmed that the cloned Arabidopsis thaliana NPRl homologous gene from rice Gui99 is involved in positively regulating SAR of rice.