Transgenic corn plants with modified ribosomal protein L3 show decreased ear rot disease after inoculation with Fusarium graminearum

Cereal crops are susceptible to various Fusarium species worldwide. Fusarium graminearum is a major pathogen of corn that causes ear rot disease and contaminates kernels with mycotoxins such as deoxynivalenol (DON). DON binds with the 60S ribosomal protein L3 (RPL3), blocking the translational machinery in the eukaryotic cells. Previously, the modified rice Rpl3 gene (resulting in a change in amino acid residue at 258 from tryptophan to cysteine) was transformed into tobacco and resulted in increased resistance to DON. In the present study, the same modified Rpl3 gene was used to develop two types of transgenic corn plants in which the modified Rpl3 gene was controlled by a constitutive 35S CaMV promoter or a silk-specific ZmGRP5 promoter. The transgenic lines were evaluated for the ear rot disease in the field by inoculating F. graminearum spores in silk and kernel tissues. The overall disease symptoms in the transgenic lines were significantly lower than wild type plants. Transgenic plants having the Rpl3 gene with 35S CaMV promoter showed a 23 to 58% decrease in disease scores whereas the transgenic plants expressing the modified Rpl3 gene under silk specific promoter showed a 27 to 62% decrease in disease scores compared to wild type plants. The kernel inoculation gave lesser disease symptoms in both types of transgenic plants compared to silk inoculation. The maximum decrease in disease scores was observed (up to 62%) in transgenic plants expressing modified Rpl3 gene with silk specific promoter when inoculations were done through kernels. The present report is the first field study of transgenic corn plants developed to reduce F. graminearum infection. Taken together, the results suggest that the modified Rpl3 gene is effective in reducing ear rot disease in corn.