2.11. Immunomicroscopy
Nodules collected at 7 and 14 dpi were processed for immunomicroscopy
as previously described (Fan et al., 2014). Briefly, sections
(70 nm thick) of nodule tissue were collected onto pre-coated gold
grids. Grids were blocked in blocking buffer, prepared with 2% nonfat
dry milk in TBST (0.3% Tris, 0.02% KCl, 0.8% NaCl, and 0.05% Tween), at
pH 7.4 for 1 h and then incubated in rabbit anti-nitrogenase antibody
(1:100 dilution). For anti-nitrogenase antibody assay, samples were incubated
in anti-rabbit IgG colloidal gold antibody, 10 nm (Sigma) (1:20
dilution). The nodule samples were stained with 0.5% uranyl acetate
and imaged using a Zeiss Libra 120 TEM (Carl Zeiss, Inc., Germany).