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Nitrogen (N) is an important nutrient for plant growth and yield production, and rice grown in paddy soil mainly uses ammonium (NH4 +) as its N source. Previous studies have shown that N status is tightly connected to plant defense; however, the roles of NH4 + uptake and assimilation in rice sheath blight disease response have not been studied previously. Here, we analyzed the effects of different N sources on plant defense against Rhizoctonia solani. The results indicated that rice plants grown in N-free conditions had higher resistance to sheath blight than those grown under N conditions. In greater detail, rice plants cultured with glutamine as the sole N source were more susceptible to sheath blight disease compared to the groups using NH4 + and nitrate (NO3 ) as sole N sources. N deficiency severely inhibited plant growth; therefore, ammonium transporter 1;2 overexpressors (AMT1;2 OXs) were generated to test their growth and defense ability under low N conditions. AMT1;2 OXs increased N use efficiency and exhibited less susceptible symptoms to R. solani and highly induced the expression of PBZ1 compared to the wild-type controls upon infection of R. solani. Furthermore, the glutamine synthetase 1;1 (GS1;1) mutant (gs1;1) was more susceptible to R. solani infection than the wild-type control, and the genetic combination of AMT1;2 OX and gs1;1 revealed that AMT1;2 OX was less susceptible to R. solani and required GS1;1 activity. In addition, cellular NH4 + content was higher in AMT1;2 OX and gs1;1 plants, indicating that NH4 + was not directly controlling plant defense. In conclusion, the present study showed that the activation of NH4 + uptake and assimilation were required for rice resistance against sheath blight disease.

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mediates early host defense against attaching and effacing bacterial pathogens Nat Med 14 282 289 . 59. K

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between glutathione biosynthesis and stress defense gene expression in Arabidopsis. Plant Cell 16 , 2448-2462. Evidence for a direct link between glutathione biosynthesis and stress defense gene expression in Arabidopsis

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Dowd, P. F. and Lagrimini, L. M. (1997): The role of peroxidase in host insect defense. In: N. Carozzi and M. Koziel (eds): Advances in Insect Control. Taylor and Francis Ltd., London, England, pp. 195

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. Horticult. 160 , 222 – 229 . 10. Cordier , C. , Pozo , M. J. , Barea , J. M. , Gianinazzi , S. , Gianinazzi , Pearson V. ( 1998 ) Cell defence responses associated with

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WG Forssmann 2003 Human hemoglobin-derived peptides exhibit antimicrobial activity: a class of host defense peptides J Chromatogr B Analyt Technol Biomed Life Sci

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( Areca catechu L.) under assam condition . The Bioscan 8 , 1291 – 1294 . Chen , C. , Bélanger , R. R. , Benhamou , N. and Paulitz , T. ( 2000 ): Defense enzymes induced in cucumber roots by treatment with plant growth promoting

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Acta Agronomica Hungarica
Authors: J. Szarka, O. Toldi, E. Szarka, J. Remenyik, and et al.

The fact that production is often unsuccessful even when resistant varieties are selected on the basis of the hypersensitive reaction can be attributed to the lack of adequate knowledge on plant disease resistance. In addition to specific plant responses to pathogen species, plants also possess an aspecific defense reaction which, instead of causing rapid tissue destruction, is based on the opposite strategy, protecting the plant against attack by microbes through tissue compaction achieved by cell enlargement and cell division. Genetic analyses carried out in pepper revealed that the general defense reaction was inherited as a monogenic recessive trait (gds). Pathophysiological observations indicate that the stimulus threshold is lower and the reaction rate faster than for specific defense reactions. Biochemical analyses suggest that, unlike plants exhibiting rapid tissue destruction, plants containing the gds gene do not require an oxidative burst elicited by hydrogen peroxide to stimulate the defense mechanism. It was also found that the regulation of the general defense system involves metabolic pathways that are independent of salicylic acid. The general and specific plant reactions form an integrated system of plant defense.

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European Journal of Microbiology and Immunology
Authors: C. Belzer, B. A. M. van Schendel, T. Hoogenboezem, J. G. Kusters, P. W. M. Hermans, A. H. M. van Vliet, and E. J. Kuipers

-responsive regulation of peroxide stress defense genes by the PerR repressor J Bacteriol 181 6371 – 6376 . 19. A. Danielli

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