Linking nitric oxide synthesis and chloroplasts functionality

GALATRO A; PUNTARULO S; GUIAMET JJ; SIMONTACCHI M

CABA

Congreso; VIII International Congress Society for Free Radical Biology and Medicine. South American Group; 2013

Society for Free Radical Biology and Medicine. South American Group

Nitric oxide (NO), as an endogenous product in plants, participates in a wide spectrum of biologically important reactions, in responses to biotic and abiotic stress, and as a component in hormone-regulated processes. However, the sources of NO, which probably rely on local substrates availability such as L-arg, O2, or nitrite concentrations, as well as changes in pH, remain unclear. We are exploring the hypothesis that the NO content in soybean cotyledons is related to chloroplast functionality in planta. Employing confocal fluorescence microscopy and electron paramagnetic resonance (EPR) we found that chloroplasts contribute to NO synthesis in vivo. Chloroplast functionality was assessed measuring photosystem II quantum yield. A correlation was found between total NO content in tissue, the detection in chloroplasts, and photosystem II quantum yield along the cotyledon life span. Besides, NO synthesis decreased in conditions that severely affected photosynthetic electron transport. These findings suggest that chloroplasts are organelles that contribute to NO synthesis in vivo, and that their proper functionality is essential for maintaining NO levels in soybean cotyledons.