NIM1 Overexpression in Arabidopsis Potentiates Plant Disease Resistance and Results in Enhanced Effectiveness of Fungicides

Abstract

The NIM1 (for noninducible immunity, also known as NPR1) gene is required for the biological and chemical activation of systemic acquired resistance (SAR) in Arabidopsis. Overexpression of NIM1 in wild-type plants (hereafter referred to as NIM1 plants or lines) results in varying degrees of resistance to different pathogens. Experiments were performed to address the basis of the enhanced disease resistance responses seen in the NIM1 plants. The increased resistance observed in the NIM1 lines correlated with increased NIM1 protein levels and rapid induction of PR1 gene expression, a marker for SAR induction in Arabidopsis, following pathogen inoculation. Levels of salicylic acid (SA), an endogenous signaling molecule required for SAR induction, were not significantly increased compared with wild-type plants. SA was required for the enhanced resistance in NIM1 plants, however, suggesting that the effect of NIM1 overexpression is that plants are more responsive to SA or a SA-dependent signal. This hypothesis is supported by the heightened responsiveness that NIM1 lines exhibited to the SAR-inducing compound benzo(1,2,3)-thiadiazole-7-car-bothioic acid S-methyl ester. Furthermore, the increased efficacy of three fungicides was observed in the NIM1 plants, suggesting that a combination of transgenic and chemical approaches may lead to effective and durable disease-control strategies.

Priming in plant–pathogen interactions

“…The fungicide-mediated resistance could be based on priming because fungicide application alone does not lead to any obvious changes in gene induction in Arabidopsis. A role for NIM1 in priming of fungicide or chemical inducer action is also supported by the fact that NIM1-overexpressing Arabidopsis plants display both potentiated disease resistance and enhanced efficacy of fungicides [58].…”

In Vivo Interaction between NPR1 and Transcription Factor TGA2 Leads to Salicylic Acid–Mediated Gene Activation in Arabidopsis

“…Overexpression of the NPR1 gene in Arabidopsis and rice rendered the transgenic plants more resistant to various pathogens in the absence of a SAR inducer or after treatment with lower-thannormal concentrations of the inducer (Cao et al, 1998;Chern et al, 2001;Friedrich et al, 2001). Interestingly, overexpression of NPR1 did not result in constitutive PR gene expression before pathogen challenge, indicating that the NPR1 protein requires activation, perhaps by SA, to be functional in PR gene activation.…”

TRANSGENIC EGYPTIAN WHEAT (Triticum aestivum L.) WITH Arabidopsis NPR1 GENE via BIOLISTIC BOMBARDMENT

“…AtNPR1 gene is a key regulator of systemic acquired resistance (SAR) and can enhance disease resistance in plants such as Arabidopsis and monocot plants (Friedrich et al, 2001;Chern et al, 2005). AtNPR1 gene confers lasting broadspectrum disease resistance to viral, bacterial and fungal pathogens (Chern et al, 2001).…”