Cross-Regulation between N Metabolism and Nitric Oxide (NO) Signaling during Plant Immunity.
Plants are sessile organisms that have evolved a complex immune system which helps them cope with pathogen attacks. However, the capacity of a plant to mobilize different defense responses is strongly affected by its physiological status. Nitrogen (N) is a major nutrient that can play an important role in plant immunity by increasing or decreasing plant resistance to pathogens. Although no general rule can be drawn about the effect of N availability and quality on the fate of plant/pathogen interactions, plants' capacity to acquire, assimilate, allocate N, and maintain amino acid homeostasis appears to partly mediate the effects of N on plant defense. Nitric oxide (NO), one of the products of N metabolism, plays an important role in plant immunity signaling. NO is generated in part through Nitrate Reductase (NR), a key enzyme involved in nitrate assimilation, and its production depends on levels of nitrate/nitrite, NR substrate/product, as well as on L-arginine and polyamine levels. Cross-regulation between NO signaling and N supply/metabolism has been evidenced. NO production can be affected by N supply, and conversely NO appears to regulate nitrate transport and assimilation. Based on this knowledge, we hypothesized that N availability partly controls plant resistance to pathogens by controlling NO homeostasis. Using the Medicago truncatula/Aphanomyces euteiches pathosystem, we showed that NO homeostasis is important for resistance to this oomycete and that N availability impacts NO homeostasis by affecting S-nitrosothiol (SNO) levels and S-nitrosoglutathione reductase activity in roots. These results could therefore explain the increased resistance we noted in N-deprived as compared to N-replete M. truncatula seedlings. They open onto new perspectives for the studies of N/plant defense interactions.
Agroécologie, AgroSup Dijon, CNRS, INRA, Université Bourgogne Franche-Comté Dijon, France.
Elise
E
Thalineau
Agroécologie, AgroSup Dijon, CNRS, INRA, Université Bourgogne Franche-Comté Dijon, France.
Hoai-Nam
HN
Truong
Institut Sophia Agrobiotech, UMR, INRA, Université Nice Sophia Antipolis, CNRS Sophia Antipolis, France.
Antoine
A
Berger
Agroécologie, AgroSup Dijon, CNRS, INRA, Université Bourgogne Franche-Comté Dijon, France.
Carine
C
Fournier
Institut Sophia Agrobiotech, UMR, INRA, Université Nice Sophia Antipolis, CNRS Sophia Antipolis, France.
Alexandre
A
Boscari
Agroécologie, AgroSup Dijon, CNRS, INRA, Université Bourgogne Franche-Comté Dijon, France.
David
D
Wendehenne
Agroécologie, AgroSup Dijon, CNRS, INRA, Université Bourgogne Franche-Comté Dijon, France.
Sylvain
S
Jeandroz
Aphanomyces euteiches; Medicago truncatula; nitric oxide homeostasis; nitrogen metabolism; plant immunity