| Pathogens are one of the prevalent stresses to plants. Resistance mediated by the resistance genes is efficient mechanism for evading the pathogens. To understand the influence of various biotic and abiotic factors on resistance gene promoters, plants having N gene promoter fused with reporter genes were developed. Experiments with tobacco plants revealed that on tobacco mosaic virus infection, the N protein may increase in the cells. Also, extreme temperature may result in decrease in the N protein. The salicylic acid produced during the development of systemic acquired resistance does not hinder the N promoter function. Hence, it can be concluded that the promoter region of resistance genes can be influenced by many biotic and abiotic factors. In the tobacco plants lacking the N gene, infection with tobacco mosaic virus leads to generation of systemic recombination signal. Experiments suggest that this signal can lead to better tolerance of the pathogen in next generation. Also, in the plants which received systemic recombination signal, the resistance gene loci are hypermethylated and the frequency of rearrangement in these loci increases. Hence, the signal results in higher tolerance to pathogen and increased genetic variability in resistance genes. |
