Jul 1, 2005

Overexpression of a rice NPR1 homolog leads to constitutive activation of defense response and hypersensitivity to light

Molecular Plant-microbe Interactions : MPMI
Mawsheng ChernPamela C Ronald

Abstract

Arabidopsis NPR1/NIM1 is a key regulator of systemic acquired resistance (SAR), which confers lasting broad-spectrum resistance. Previous reports indicate that rice has a disease-resistance pathway similar to the Arabidopsis SAR pathway. Here we report the isolation and characterization of a rice NPR1 homologue (NH1). Transgenic rice plants overexpressing NH1 (NH1ox) acquire high levels of resistance to Xanthomonas oryzae pv. oryzae. The resistance phenotype is heritable and correlates with the presence of the transgene and reduced bacterial growth. Northern analysis shows that NH1ox rice spontaneously activates defense genes, contrasting with NPR1-overexpressing Arabidopsis, where defense genes are not activated until induction. Wild-type NH1, but not a point mutant corresponding to npr1-1, interacts strongly with the rice transcription factor rTGA2.2 in yeast two-hybrid. Greenhouse-grown NH1ox plants develop lesion-mimic spots on leaves at preflowering stage although no other developmental effects are observed. However, when grown in growth chambers (GCs) under low light, NH1ox plants are dwarfed, indicating elevated sensitivity to light. The GC-grown NH1ox plants show much higher salicylic acid (SA) levels than the wild type...Continue Reading

Mentioned in this Paper

Systemic Acquired Resistance
Xanthomonas oryzae
Biochemical Pathway
Rice (Dietary)
Photophobia
Arabidopsis
Xanthomonas albilineans
Homologous Sequences, Amino Acid
Gene Expression Regulation, Plant
NPR1 gene

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