Abstract
In Arabidopsis, non-expressor of pathogenesis related genes-1, NPR1 has been shown to be a positive regulator of the salicylic acid controlled systemic acquired resistance pathway and modulates the cross talk between SA and JA signaling. Transgenic plants expressing AtNPR1 constitutively exhibited resistance against pathogens as well as herbivory. In the present study, tobacco transgenic plants expressing AtNPR1 were studied further for their response to infection by the sedentary endoparasitic root knot nematode, Meloidogyne incognita. Transgenic plants showed enhanced resistance against the root-knot nematode infection. Prominent differences in the shoot and root weights of wild type and transgenic plants were observed post-inoculation with M. incognita. This was associated with a decrease in the number of root galls and egg masses in transgenic plants compared to WT. The transgenic plants also showed constitutive and induced expression of some PR protein genes, when challenged with M. incognita.
Highlights
In Arabidopsis, non-expressor of pathogenesis related genes-1, NPR1 has been shown to be a positive regulator of the salicylic acid controlled systemic acquired resistance pathway and modulates the cross talk between SA and JA signaling
Root-knot nematode species including Meloidogyne incognita are amongst the most destructive plant parasitic nematodes infecting almost all cultivated plants and are responsible for yield losses amounting to billions of dollars [1]
The complex morphological and physiological changes that occur during the establishment of feeding sites by these intruders are reflected in altered gene expression in the host [2]
Summary
Root-knot nematode species including Meloidogyne incognita are amongst the most destructive plant parasitic nematodes infecting almost all cultivated plants and are responsible for yield losses amounting to billions of dollars [1]. The high expression line, 19-1 showed high level of resistance to nematode inoculation when compared to other plants This could be correlated with the constitutive expression of the pathogenesis related proteins and the genes for antioxidant enzymes like ascorbate peroxidase and super-oxide dismutase by the NPR1 transgenic plants [8]. The gene expression got further enhanced upon treatment with the nematode (Figure 3) These observations indicate that the resistance to the nematode exhibited by Figure 2 Development of root knots (a) and egg masses (b) in the tobacco wild type and transgenic plants six weeks after infection with the nematode. The constitutive basal expression as well as induced level of PR1 and PR5 in the present study along with the constitutive expression of genes for oxidative enzymes [8] was probably associated with enhanced resistance observed against the M. incognita in AtNRP1 expressing transgenic tobacco plants These observations demonstrate the versatility of NPR1 protein in providing multiple stress tolerance in crop plants. The actual mechanism by which AtNPR1 confers resistance to the target nematode remains to be worked out in detail
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