EXPRESSION OF STEARATE AND OLEATE DESATUR ASES IN SUNFLOWER AND HIGH OLEIC SUNFLOWER - CLONING OF GENOM FRAGMENTS AND VARIABILITY IN DIFFERENT HELIANTHUS

The steady state levels of sunflower (Helianthus annuus I, var macroca rpus) transcripts, detected with heterologous probes to either the Del ta 9, or the Delta 12 desaturase was determined in immature seeds and vegetative tissues at different stages. The transcripts of the Delta 9 and the Delta 12 genes were mainly detected in immature embryos betwe en 12 and 20 days after pollination, and weakly in the other tissues e xamined. The accumulation of Delta 9 gene transcript precedes that of the Delta 12 gene, and coincides with the onset of delectable enzymati c activities. The levels of mRNA accumulation in CANP3, a line with no rmal level of oleic acid, and a high oleic acid line (HOC) were compar ed after standardization of signal intensities. The Delta 12 mRNA accu mulation was significantly reduced in HOC in comparison with CANP3. In the HOC varieties, the Delta 12 enzymatic activity is considerably re duced in seeds whereas it is maintained in leaves. The HOC mutation is correlated with a reduction in the steady slate level of a putative s eed specific Delta 12 gene. We also observed that the Delta 9 and Delt a 12 mRNAs accumulate to higher levels in developing seeds maintained at 26 degrees C day/22 degrees C night than at 20 degrees C day/18 deg rees C night. From a genomic library 2 and 4 clones carrying homologou s sequences respectively to the Delta 9 and the Delta 12 desaturases, were used for amplification with primers unique to each desaturase. Th is enabled us to clearly identify such desaturases. Moreover we applie d the couple of primers unique to the Delta 9 desaturase to amplify fr agments in 12 different wild species covering most of the Helianthus. Sequence variability revealed a mixture oi two Delta 9 sequences in al l the species of Helianthus.