Chloroplast Functionality Has a Positive Effect on Nitric Oxide Level in Soybean Cotyledons.

GALATRO A., PUNTARULO S., GUIAMET J.J., SIMONTACCHI M.

Plant Physiol. Biochem

Elsevier

Lugar: Filadelfia; Año: 2013 vol. 66 p. 26 - 33

0981-9428

The sub-cellular localization of NO generation in soybean cotyledons, and the relationship between NO synthesis and in vivo chloroplast performance were studied. Fluorescence microscopy, employing 4-aminomethyl-2´,7´-difluorofluorescein diacetate (DAF-FM DA), showed a strongly punctuated fluorescence in mesophyll cells. The co-localization of DAF-FM and chlorophyll fluorescence, in confocal laser microscopy images, indicated the presence of NO in the chloroplasts. NO visualization was dependent on light irradiance, seedling age, and chloroplast function throughout cotyledons lifespan cycle. The addition of herbicides with action in chloroplasts (DCMU and paraquat) dramatically affected the quantum yield of photosystem II (fPSII), and lead to images with absence of punctuated green fluorescence. Moreover, electronic paramagnetic resonance signals corresponding to NO-spin trap adduct observed in cotyledon homogenates decreased significantly by the treatment with herbicides, as compared to controls. Neither chloroplast function nor NO content were significantly different in cotyledons from plants growing in the presence of ammonium or nitrate as the nitrogen source. 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.