Sugars as a metabolic regulator of storage protein mobilization in germinating seeds of yellow lupine (Lupinus luteus L.)

Abstract

The intensity of protein reserve activation in yellow lupine (Lupinus luteus L.) organs cultured in vitro in the presence of saccharose and without sugar in the medium was studied. Isolated embryo axes, excised cotyledons and seeds deprived of their testae were grown on Heller medium: a) with 60 mM saccharose (+S), b) without sugar (−S) and c) for 72 hours without saccharose + for 24 hours in the presence of saccharose (−S→+S). Using nitroanilide substrates, exo- and endopeptidase proteolytic activity was investigated in enzymatic extracts. Proteolytic activity was examined in organs isolated from swollen seeds and also in organs cultured for 24, 48, 72 and 96 hours. The proteolytic activity was higher in organs cultured on medium without saccharose. Stimulation of the proteolytic activity on the first day of culture was not significant, but intensified in the successive days of culture. The organ subcultured onto a medium with saccharose (−S→+S) caused a significant limitation of proteolytic activity, even to a markedly lower level in comparison to that activity level in the material continuously supplemented with saccharose. Observations of ultrastructure in Transmission Electron Microscopy revealed increased protein body degradation in the absence of saccharose in the medium and an increased degree of cell vacuolization, which may be indicative of intensifying autophagic processes under conditions of carbohydrate deficit.