EXPRESSION OF MESSENGER-RNA AND STEADY-STATE LEVELS OF PROTEIN ISOFORMS OF ENOYL-ACP REDUCTASE FROM BRASSICA-NAPUS

The expression of mRNA and the steady-state levels of two-component en zymes of plant fatty acid synthetase (FAS) were studied. Northern anal ysis of enoyl-ACP reductase (ER) and stearoyl-ACP desaturase (SD) gene expression showed that steady-state levels of both transcripts increa se during lipid deposition in the seed reaching a maximum al 29 days a fter flowering (DAF). The steady-state level of ER message falls very quickly after reaching its maximum, whereas the SD message is longer-l ived. The levels of these specific mRNAs in seed are 15-30 times great er than in leaf. Optimum mRNA expression precedes the maximum levels o f synthesis of the two proteins, which in turn precede the maximum lev el of oil. The expression of isoenzymes of ER were examined by two-dim ensional western blotting in both leaf and seed tissue. Four enzymes a re expressed in both of these tissues; the two most abundant isoforms in seed material are also the most abundant in leaf tissue.