Detection of Nitrosyl Iron Complexes in Sorghum Embryos

SIMONTACCHI, M; JASID, SEBASTIÁN; PUNTARULO, S

Santiago de Chile

Congreso; VI Meeting of SFRBM South American Group: Free Radicals and Antioxidants in Chile 2009; 2009

SFRBM_South American Group

It was previously described that sorghum embryonic axes produce detectable amounts of nitric oxide (NO) 24-30 h after seeds are allowed to germinate under physiological conditions. S-nitrosothiols and nitrosyl iron complexes have been proposed as stable NO carriers capable of transporting NO to a distance several fold exceeding cell sizes. Homogenates from sorghum embryonic axes exposed in vitro to NO donors (1 mM SNP, GSNO or DETA NONOate) lead to the generation of mononitrosyl iron complexes (MNIC) and dinitrosyl iron complexes (DNIC), that can be detected by electron paramagnetic resonance (EPR). These data suggest that the axes can synthesize both kind of complexes under conditions of high NO availability. In embryonic axes isolated from seeds after 24 h of incubation in the presence of NO donors, only the MNIC signal was observed and the presence of DNIC could not be confirmed by EPR under these experimental conditions. In axes that were exposed in vivo to 1 mM SPN, the spectrum corresponding to MNIC disappeared after treatment with deferoxamine, with a concomitant increase in the signal for Fe(III). In summary, these results showed that i) both MNIC and DNIC can be generated during in vitro incubation of sorghum homogenates under high NO availability, and ii) MNIC can be formed in vivo in sorghum embryonic axes. Moreover, since previous data from our laboratory showed that the amount of DF-Fe(III) complex is higher in NO donors exposed embryos as compared to controls, a role for NO in iron mobilization in plants can be suggested. Supported by grants from UBA, CONICET and ANPCyT.