Effect of Rib5P, Fru1,6bisP, 3PGA, and Glc6P on wheat endosperm SnRK1 activity. The principal effectors were evaluated at different concentrations by analyzing phosphorylation of np-Ga3PDHase in the presence of 5 mm Mg2+. Top, Schematic representation; bottom, autoradiographs. One hundred percent corresponds to the respective phosphorylation obtained in the absence of effector in each case. Values are the mean figures resulting from three different determinations reproducible within ±10%.