Abstract
Nitric oxide (NO) has been shown to be an important messenger in plant defense signaling against microbial pathogens. NO participates in the induction of the hypersensitive response (HR), defense gene expression and production of antimicrobial compounds. NO generating systems in plants are obscure. Nitrate reductase (NR) is an enzyme capable of producing NO in plants. Silencing NR genes from Nicotiana benthamiana resulted in significant decrease of NO production induced by INF1, a major elicitin secreted by Phytophthora infestans, suggesting that NR is responsible in part for NO production in plant defense. However, the possibility remains that other NO-generating system(s) contribute to NO production. Only the gene for Arabidopsis thaliana nitric oxide-associated 1 (AtNOA1) has been identified as a putative regulator of NOS activity in plants. NbNOA1, a homolog of AtNOA1, is involved in INF1-mediated NO production and is required for defense responses.
