COMPOSITIONAL CHANGES AND STORAGE PROTEIN-SYNTHESIS IN DEVELOPING SEEDS OF BRASSICA-CAMPESTRIS

The growth and compositional changes of developing seeds of Brassica c ampestris var. B9 were followed from the early stage after anthesis up to maturity, grown under field conditions. Seed dry weight, nucleic a cid, lipid and protein accumulation followed almost a sigmoidal patter n, but were not in phase. While DNA and RNA accumulation slowed down e arlier, protein and lipid accumulation continued up to the dehydration stage. Again, significant lipid accumulation started later than prote in, but continued even after protein accumulation ceased. The major cl asses of storage protein (12S and 2S) were appreciably synthesised two weeks after flowering. The levels of mRNA for 2S seed protein as dete rmined by slot blot and northern hybridisation with labelled cloned 2S napin cDNA as probe paralleled the rate of protein accumulation. Inco rporation of [S-35]-methionine in mid - maturation stage seeds in vitr o indicated that all of the major types of seed storage proteins are p robably synthesised as precursors, which are then processed to mature seed proteins.